I'm more interested to hear stories about non-game software, but game developers can also share their thoughts,
That being said: why not? For Apple, the App Store is great. It shows you what is popular and what others find useful. It adds a layer of social proof to your applications. I was using an HTTP REST client for the longest time that was a pain in the ass to use. A lot of user interface inconveniences existed. After Google failed me, I cracked open the App Store and was fortunately able to find the app Rested. It's not perfect in my opinion, but it's been a breath of fresh air when developing my API.
We can argue all we want on the walled garden approach of the App Store, but it's a great platform. We also need to remember that it's still an infant, and it's going to evolve and improve. The more we use it when building software, and the more our customers and users use it to discover and rate our stuff, the better it will become. Apple certainly doesn't let the community dictate their moves, but they certainly allow us to influence their decisions if enough people are on board.
For this reason, I think you should definitely start using the Ubuntu software center. If it provides a simple and more pleasant experience for your users, great! Hopefully there will be more and more people looking at desktop Linux in the future who will need a place to find applications. If you can help evangelize and shape their platform with the weight of a successful app, then the whole ecosystem will grow and flourish from it.
Personally, as a user of Ubuntu, I never use the Ubuntu Software Centre - not even for free software - I much prefer apt-get, and I'm not aware of anything (aside from paid software, which I didn't even know about until you mentioned this) that Ubuntu Software Centre does that apt-get doesn't.
1) Keeps track of system state. Tracks packages installed as dependencies, and remove them when necessary meaning no orphaned packages.
2) Handles recommends well. apt-get fails to handle recommends, which many packages depend on to pull in dependencies.
3) Searching. More intuitive and better formatted than apt-cache search. There is also the text UI when running aptitude directly. For example, how do I find all installed python packages?
$ apt-cache search python
Returns all packages with python in title or description.
$ aptitude search '~ipython'
$ aptitude search python | grep ^i # installed packages are flagged with i on the first line
to look for packages that you have installed use "dpkg -l"
aptitude is otherwise great and I prefer it over apt-get
$ aptitude search '~dautojump'
p autojump - shell extension to jump to frequently used directories
p jumpapplet - autojump notification icon, to jump to frequently used directories
I understand the reasoning in this, the only downside is that it means if I've started to use something that only got installed as a dependency, it can disappear without warning.
"More intuitive and better formatted than apt-cache search."
This is neat, I may start using it.
To be honest, a lot of people have recommended aptitude to me over the years, but I've never seen enough of a benefit to try to override my muscle memory. I guess it's a classic "bicycle problem".
Is this the same as:
If a package depends on a recommendation, then that sounds like a packaging bug. Report it to the package maintainer.
Chose that game after seeing it in the Steam client, but wasn't able to buy it for Linux there.
Great game by the way.
I'm selling the same app on both Ubuntu Software Center  and Mac App Store . Between June and December I have sold 29 licenses on Ubuntu store and ~2000 licenses on Mac App Store.
Chrome Web Store  seems to be a much more promising distribution channel for Linux apps. With the new APIs it will be possible to access native window manager, USB ports, filesystem or webcam. Besides, you don't have to deal with incompatibilities between distros.
What I've been looking into this today...It seems that it's not really worth it, as you said. I would kind of want it to worth it, maybe some day it will be.
Not to mention that the UI is kinda slow and clunky.
Basically gives the feeling of being in a neon lit discount store rather than a premier software showroom.
I think it might do better to get rid of it as an application altogether and just build an attractive webpage that gives a lot of space over to highlighting the best, most polished commercial apps with a handful of the higher quality open source desktop software. Use a browser plugin to trigger installation.
Installing open source libraries, dependencies and dev tools could be handled by a more utilitarian ncurses front end to apt or something.
I'd be curious to know if it is worth it as well. Have you spoke with any commercial developers directly?
If you want to sell for Android (which is, of course, a type of Linux), try the Google or Amazon app stores.
Dominions 3 , a commercial game with a native Linux build, recently changed publishers and is now sold on Desura .
If you enjoy making your users put up with horrible DRM, I've seen multiple HN articles about how Linux support for Steam is in the works.
It's an open beta right now with about 40 games listed under Linux.
Regarding the Super Meat Boy issue, here is a response from David Pitkin who runs the Ubuntu Software Center at Canonical and works with developers:
"I just looked into it and the check to Tommy and Edmund from Canonical is in process for the 77 copies of Super Meat Boy. We have been working together since November to get it resolved, no piracy here just some miscommunication".
So went to find software center - not in the classic menu, but entering software-cetner got it from the terminal.
Seems it suffers like all the others, only one level of hierarchy, looking for Desktop publishing, select office and start reading through the hundred plus entries, most of which have a clever name and icon which does nothing to relate it to desktop publishing at all.
You want o make big bucks at your app, help develop better app stores, so people can find your app.
Also, I avoid the Ubuntu Software Centre as much as I can. I find the Ubuntu desktop to be atrocious and I log in via ssh as much as I possibly can to Ubuntu machines.
If there's any market here it would be for a $500+ product that customers want bad enough to deal with the USC than it would be for $5 games; even in that case most of your marketing work is going to be outside the USC.
Why hasn't anybody come out with a Linux distribution that contains an Android personality so that you can run Android apps side to side with normal Linux apps kinda like Windows 8? It seems Linux could use this to close the usability gap with other OSes.
For example check the Humble Bundle: Linux users always pay more than average.
Although I'd not sell in the Ubuntu Software Center: As you would miss a lot of users from other distros (or people who don't use the Software Center).
Software that runs on Linux that I've seen people pay for:
Accounting and Bookkeeping
Medical Billing/Practice Management
POS/Retail Inventory Management
Industrial Control Management Interfaces
Are you seeing a theme? Boring useful software that needs to be maintained to keep up, and software that talks to other systems.
There are still a lot of things that don't seem ready for prime time for the consumer market in Linux distros, and I wish it wasn't like that.
It's a pretty ugly piece of software with unrefined edges all over the place but it gets the job done for now. That being said I've never bought anything through the software center, just installed free software.