Ahhhh a question right up my alley.
I just purchased an Asus A7N8X Deluxe board and I love it.
how good is the Asus A7N8x ??
I love the board. The board layout is good and the deluxe version comes packed with features. I have a total of 6 USB ports, 4 on the back where the I/O shield goes, 2 firewire ports available onboard through a bracket and a cable, not 1 but 2 RJ45 jacks, one is a 3Com NIC, the other is the nVidia NIC, both are exceptional. It's got a total of 6 audio connectors on the back (front/line out, rear, mic, line in, S/PDIF, center channel). The features of the board are so cool.
supports 333/400 fsb, this is backwards compatiable right ? if i get the 266fsb ?
Affirmative, running a 266fsb XP 2200+ in mine right now and it runs perfectly fine.
the agp slot is backwards compatiable to right?
It supports 1.5V cards...so some older cards may not work. What is cool, with at least the Deluxe, there is a red LED that lights up if the card is not valid.
IS IT STABLE ?
Better than my Shuttle AK35GTR. I have not had a single problem with the board installation nor setup or anything. No crashs or anything. There is a Speech Reporter that tells you what the problem is when you use the onboard sound. One thing I am experiencing, however, is that supposedly my system fails CPU tests when playing 3d games. This is a problem with my cheap 500W CompUSA brand PSU, which will be replaced.
Ask any more questions/concerns with this board.
I will probally be useing a AMD XP2400.. First off,this board says supports 333/400 fsb, this is backwards compatiable right ? if i get the 266fsb ? second, the agp slot is backwards compatiable to right? i havent used an 8x board yet 
Third, IS IT STABLE ? Thanks fer ur help