The issue is not with the promotion itself, since the marketplace handles that and drives the customers to you. When a new theme is released, if it's good/attractive enough, it'll get many many sales. Then, you should provide ongoing support to your items. When you have 1-2 themes that's good, but having 6 or 7 themes, all of them with ongoing support turns out quite hard to maintain.
Eventually, the themes stop selling, unless you've created some sort of product that sells like hotcakes all the time (there are a few). But, most of the themes sell for a few weeks/months then you have to start working on a brand new product again, to keep up with the competition, and to promote your previously released products.
I had issues scaling the business since I was not able to cope with the amount of work that needed to be done (and also because I couldn't find anybody competent enough to provide support / fixes). That is, provide support on the forums, bug fixes, stability & compatibility updates, and releasing new themes. Not to mention having 0% time to work on side projects.
It's not a fire and forget scheme, each product has its own ongoing support service that has to be provided. There are people that purchase the theme just because of your support, not mainly because it looks good enough. For a single person (doing everything) becomes quite a lot to handle, even if the profits are quite lucrative.
If all you ever want to do in your life is sell themes, then the marketplace is great for you. I'm aiming at a more self-managed project, such as a SaaS product, or my own startup, not planning to live out of the themes business, which was one of the reasons why I've decided to stop.
MVC Web Framework for NodeJS written in CoffeeScript.
This is an open source project that has just been released, and from my experience developing it, here are my conclusions:
I believe some people are comfortable coding one way, and others are comfortable coding another. Anyways, everybody uses what works. At the end, the productivity you've got and the time you save is all that matters.
Regarding the issue with the stack traces and CoffeeScript, you're right, line numbers are not accurate, but if you know where the problem is and you'll know how to debug it, on the spot.
I was not attracted to CoffeeScript myself when I first saw it, but after having a closer look, I finally realized it is a great tool to use when applicable. Then I decided to migrate the whole code to CS.