Before you sink too far into despair, let me say: not everything is hopeless.
Firefox is mostly okay. I use Firefox 2 and Firefox 3 on different machines on a daily basis, and I'd be hard-pressed to tell you why you need to upgrade. I can name a few things that are different, but I don't know that they're necessarily better. But Firefox 3 isn't so much worse that I'm cursing the mother that bore it, and that's pretty good for a Linux desktop application major-version upgrade.
The GNOME System Monitor doesn't seem to change much, especially considering how often it's mentioned in the release notes ("now with extra Cairo!"), but it's every bit as "okay, I suppose" as it ever was. I think whoever writes the release notes either needs to concentrate more on stuff real people would care about, or, conversely, has an excellent feel for their audience.
The weather/calendar/date/time/world-clock applet (yes, all those things really have merged into one) is equally, well, "okay".
I use Terminator as my terminal emulator, and it's worth pointing out that it runs better on Linux than on any other platform. Fundamentally, Linux is a good platform to develop for. I use Evergreen as my editor and it, too, runs better on Linux than on any other platform. But, important though they are to me, those are two applications by developers for developers. I'm not presenting them as examples of good Linux desktop applications, suitable for the mainstream. It's okay to expect their users to understand regular expressions and know how to write scripts and all that, and their users are people for whom "Python scripting interface" or "rewritten in Objective MonkeyPoop 7.3" might actually be a feature (the kind of crap you see all too often on the web pages of Linux music players, say).
Terminal emulators and IDEs, despite what we developers might think, aren't core parts of the desktop that everyone from beginner to expert needs to be able to use, and they're not apps it's important to come to a "good enough" consensus on. They're sovereign apps that the people who use them use day-in day-out for years. These people are prepared to devote significant time and effort into learning how to best use them, because it pays off, and they know it. Everyone has their own sovereign application. Yours might be Photoshop. His might be Word. Hers might be Keynote.
I fear for all of those people, but the Linux desktop is years or decades away for them, so maybe it doesn't matter. The people we could usefully reach are the people for whom the web browser is the sovereign application.
Most people wouldn't know a terminal emulator or an IDE if it bit them, and that's as it should be. I don't know how to drive, you don't know how to spacewalk, and that guy creeping up behind you with the knife isn't a hairdresser. These are specialist skills, often requiring specialist tools, corresponding to sovereign applications. We do all know how to open doors, climb stairs, and use toilets. These are non-specialist skills requiring no specialist tools, and correspond to things like calculators and mp3 players.
Notice that it's depth rather than subject area that's important; a calculator isn't a sovereign app, but Mathematica is. An mp3 player isn't a sovereign app, but Logic Pro is.
There's another simple rule of thumb for distinguishing the two kinds of app, and it's this: if Apple or Microsoft will sell you an application separate from their OS, it's a sovereign application. If they give it to you for free (including new versions; the first iPhoto is always free, just to get you hooked), it's not a sovereign application.
Funnily enough, one of the most frequent problems with non-sovereign applications on Linux is that they think they're sovereign applications. More about that in the next post.