Well, I am running an AirPort card and a graphite base station and i have having no problems at all. I can;t decide if I like the new Admin Utility, it seems like nothing has changed except that there are a few different ways to look at the same info now.
Slightly cooler/more "mature" interface (various views) but unless you are running AExtreme, there are no additional features that are obvious (although Apple says that the new software/firmware does fix some problems reported with specific ISPs). I noticed that the 3.0 upgrade reverted a behaviour in the menu bar where the name of the network scrolls for a few seconds. This was present in the previous software but was lost in 10.2.3 and 4 until this update (at least on my machine).