After running both 6956 and 6801 on my computer, I can tell you that 6801 is a suitable Vista replacement. It being much faster, lower on the RAM, and in general more stable. It also *shock* has better backwards compatability than Vista. 6956 (which I am running right now) has a nicer taskbar. That's about it. As a tradeoff for that, it is 20-25% slower than 6801. True both are faster than vista, but if things keep slowing down at the speed they are, Windows 7 will be only marginally faster than Vista, if faster at all. And certainly not as stable.
I haven't run any *real* benchmarks yet, but when I have I will post them here. Right now I have 6956 installed and will bench that, then format that partition and run the same benches on 6801.
*DO NOT ASK ME FOR COPIES OF THE INSTALLER DISCS I USED* If you really want them that badly google them.