Bit of a random question, but do you guys have the notorious PCI-E Gen2.0 bug if using an nVidia card on these motherboards?
If you are unsure what to look for download GPU-Z from here. If your card's PCI-E link width does not read like this screenshot

Then you have the bug.
I have been collecting data from lots of people, we have found that most ASUS boards (but not all), are effected by this bug. My P5E3 has this bug, unless you "trick it" with a 9800GX2, or GTX 295 (then the NF200 reports it's own PCI-E Link width), however with 8800GTS 512, GTX 280 and GTX 285 link with is locked @ 1.1.
ASUS claim this is because "X38" is not a PCI-E Gen 2.0 board and that there is some sort of BIOS bug (confirmed by nVidia) preventing this from working, ASUS themselves are not really bothered about fixing it, despite PCI-E Gen 2.0 being an advertised feature of the board.
I am curious to see whether your boards are effected too, as the data I have collected so far is that some X48 and even X58 ASUS boards are effected by this bug, yet ASUS are willing to brush it under the carpet and blame Intel/nVidia.
John