The problem with Mac vs PC in the old days was threefold:
1) Device drivers
2) Enterprise LOB apps (think VB)
These three concerns actually probably played a much larger role than app availability in the mid-90s. Apple stagnating the late 90s made it a no brainer. But now with OS X (1) has been knocked off the table. Notice no one talks about the much larger PC app ecosystem. Because it really doesn't matter once you get beyond a reasonable number of apps on the platform.
For this reason, I have no problem recommending a phone based on how well it nails the basics. My MIL has no clue what Color is, nor will she likely ever miss it.
Citing: "Line of business (LOB) is a general term which often refers to a set of one or more highly related products which service a particular customer transaction or business need."
Like the old, 80% of users only use 20% of the features. But it's a different 20%.
What @dhh's argument reduces to, is that the long tail doesn't matter. But only, it really does. But as you say, the long tail is what makes it a great UX for users.
I like apps and in particular I like games. I spend a decent amount of time on the train every day standing up so reading would be unpleasant for me. I listen to music or play a simple game while I ride to pass the time. The people who produce those games provide me a real service.
Apps are better on Symbian than they are on iOS they're just not as shiny.
A certain category of Symbian apps may be better than their iOS equivalents, but some other categories such as games are way better on Apple devices, and this situation is not going to change tomorrow. The fact that game studios are right now hiring iOS (and Android) developers is a sign. Even here in Japan, I've been seeing more and more job offers for iOS developers, while I can't recall any Symbian offer.
There are also the social apps that tend (at least from a personal point of view) to be much more usable on iOS than on Symbian. Take the Facebook app as an example.
Maybe s2putty is better than Prompt for iOS, but is it really a million times better ? You may not be the target for those 400'000 apps, but saying Symbian apps are better is not right.
Nokia is marketing Qt as the N9's development platform. They're also porting Qt to their S40 platform which is powering "the next billion". Apps written for these devices should (hopefully) also run on the N9.
The N9 is based on Maemo, which already has a few thousand open source apps for it. These apps will need porting but as Maemo 5 and 6 are quite similar this shouldn't be too difficult. This includes Python, PHP, Ruby, Emacs, vi and loads of other cool stuff (for people like me, at least).
There is an Android port (called NITDroid) for the Maemo 5-based N900. This doesn't currently let you make / receive phone calls but it can do everything an Android tablet can do and thousands of Android apps can be installed on it. I would be suprised if someone hadn't got NITDroid working on the N9 within a couple of months of launch.
Being Linux, Maemo runs many standard Linux programs if they are recompiled. I have The Gimp and Netbeans on my N900, for example. I can also chroot into a standard ARM Debian install and run Apache & MySQL. People will probably have Ubuntu running on the N9 soon.
As for games, Maemo shares quite a lot of its architecture with WebOS and many WebOS games run on the N900.
For the app consuming community most of the apps we get are cheap/free impulse buys that are never meant to be anything more than tiny bits of consumption, no different from that book, magazine or toy which people bought to amuse themselves during the boring parts of life. Life goes on without them but it sucks a little less with them.