[mattgreenrocks]

Yeah, it just seems like it is hard to write an app that less-experienced users will both appreciate and use...much less pay for. After all, they may think MSN Messenger feels like it was written for twelve year-olds, but do they care enough to switch? Do they even know how to look for a replacement? (IM might be a bad example as nobody wants to pay for a client on any platform, it seems.)

OS X appears to simply have more of a tradition of independently-written, beautiful software.

[gvnonor]

Well, in most cases they want a real good reason to switch and the software must market itself as a replacement. Case in point Firefox and Chrome gained a lot IE6 users by

1.Having multiple tabs which is the killer feature

2.Marketing themselves as a secure and less-crashy alternative.

This might seem like an unfair example(not everyone has Google's or Mozilla's muscle) but the basics are the same for any type of software and given sufficient effort and planning, they can compete in competitive markets with established players.