Some Problems
Immediately after upgrading to 10.5.2 I started having connect issues with my Airport Xpress base station. Every 15-30 minutes my connection to the network would be severed and take a few seconds to re-establish. Extremely annoying to say the least.
I tried rebooting my modem and base station as well as my computer, and that helped slightly, but I continued to have sporadic connect issues.
This morning I checked and noticed I was on old firmware for the base station, and corrected that. No problems since then, so I'm hoping it was just the firmware problem. I've heard of similar network issues for Macbook Pro users, but not from desktop models yet.