How did you put your own nVidia drivers in?
I went to the nVidia site yesterday, and couldn't find any Mac Drivers. So, I'm guessing our only options are Apple's included drivers?
I'm noticing weird screen "tears" when dragging the window since 10.5.4 now. Not major. But visually displeasing.
When dragging windows, a portion of the window will tear and split then reassemble on two different points on the screen. Like I suddenly hit an invisible screen split that fixes itself.
I just did a completely fresh 10.5.4 install, and know that it's not my other software or weird configurations. Reinstalled 10.5.0 from the CD and jumped straight to 10.5.4 with the combo updater.
As for WiFi, that has always sucked with OS X (well, at least since 10.4.x). I can't find the nearby connections with my Mac Pro at all (even a computer in the same room). But, if I boot into Windows Vista (on the same Mac Pro), I can find a neighbors WiFi network, and he's a half mile away from me (my closest neighbor). The same is true of my wife's iBook (stuck in OS X obviously) can't see anything local, but her Windows laptop pulls up the neighbors WiFi.
Otherwise, I don't have any stability issues with OS X. But, then I've been using it since 10.0.0. And, never had any crashes with any of the versions. Now, if you want crashing, you should have tried System / Mac OS 8.0, 8.1, 8.5.x, and 9.0 (9.2.2 was almost usable if you didn't want to do more than one thing at a time).
Instructions on restoring the old drivers can be found here. Though, honestly, with all the other problems I might just recommend simply reverting to 10.5.2 with archive and install and the combo updater, followed by Leopard Graphics Update 1.0. As for Wifi, I didn't really see any problem in 10.5.2, and at least I was connecting and not crashing. As for Mac OS before OS X, everyone knew how horrid THAT was, and that's why I never even considered touching Macs until Tiger.