I still find myself thinking "ooh, ahh" when I launch a win32 app in Wine and it just works.
It's not just you. Even my professors think it's pretty cool that I can fire up Windows apps inside Linux while all of my terminals with their garish Vim syntax highlighting continue to stare at them :-)
Wine has, over the past two years or so, become quite usable for a couple of things that I used to have to reboot (or boot my lappy) for. Internet Explorer 6 and 7 run well under Wine, which makes cross-platform testing websites much nicer. It's not perfect, as ActiveX controls don't work, but it does allow one to check to be sure your HTML and CSS and JavaScript is IE bug-compatible, though I sometimes still worry whether I'm seeing a Wine bug or a bug in my own code, when things don't work right (usually it's in my code).
I also use it to play Dwarf Fortress. It, unfortunately, doesn't do very well with any of the other Win games that I occasionally play.
Unfortunately, Safari for Windows doesn't appear to work properly in Wine. It might be possible to wrangle with it sufficiently to convince it to work, but I eventually just went with installing XP in a VirtualBox VM.
I usually just test in Konqueror and periodically test on my girlfriend's MacBook. Since Konqueror shares lineage with Safari for HTML+CSS+JavaScript, it at least looks similar most of the time...I think WebKit has actually been merged in recently, so the closeness of the two may get better.
So, it's a problem, but it's not as big a problem as not being able to test quickly and easily on IE. IE is the bitch that never works right...at least Safari's deficiencies are relatively well understood and rarely hateful (they're usually just limitations and not-quite-there standards support, rather than horrifying rendering bugs that conflict dramatically with the standards).
Can anyone who has both used Wine and run Windows under virtualization on Linux comment on the trade-offs between those approaches? It seems like virtualization works more reliably, and with at least reasonable performance.
Virtualisation is definitely more reliable, but if you need just that one Windows app, then the overhead and interface discontinuity can be annoying.
Wine also supports OpenGL, so if your app (or game..) uses that, Wine easily beats any VM solution I've tried. It also implements part of Direct3D on top of OpenGL, but that's substantially slower. Still better than no D3D support as in most VM packages, of course.
Cheers to the Wine dev team for all their hard work.