What a difference RAM can make. I just dropped an additional 1GB of RAM into my Mac (now 1.12GB total) and things are way more responsive. OS X used to struggle with more than 2 or 3 apps open at a time, but now things happen when I ask them to even with 10 or more applications running. I can even use Exposé reasonably. It still takes unreasonably long (IMO) for “Date & Time” to open, but I don’t use it enough for that to matter.
Other things of note…
I’ve solved my mouse problems thanks to USB Overdrive. OS X’s default mouse movement and acceleration are unbearably slow, even at the fastest settings (acceleration isn’t even adjustable). USB Overdrive gets me as close to my Windows mouse preferences as possible.
I still need my Windows machine for printing. Without a parallel port on the Mac, my HP LaserJet printer is all but useless. I’ve seen parallel-usb adapter cables, but I’ve heard both bad and good things about them, so I haven’t made that leap yet.
Floppies are also still an issue. Not so much with me (I tend to use FTP servers as intermediate storage to transfer files between machines), but my girlfriend likes to be able to bring her floppy from home and use it on my computer. I’m still not sure what the best solution here is — perhaps a rewritable CD drive.