Do you happen to work for Intel and/or Rambus???
1) Intel Xeons perform better only on SOME applications. Apparently, the P4 is finally coming around to performing like it's supposed to, but it's only take Intel about a year and a half to get there, which, in the meanwhile, has created a small, but growing number of people preferring AMD instead.
Low cost, topped with performance makes it a "wiser" CPU choice.
2) DDR SDRAM has A LONG way to go. DDR-I standard is JUST about to be end of lifed, making way for the DDR400 or DDR-II standard. (They're still trying to figure it out in what I presume would be JEDEC.) The ONLY reason why Rambus is even still around is because they have a couple of contracts with Intel doing other things as well.
If RDRAM was so great, interesting to note how pretty much the entire memory industry is moving just about everything to DDR. Not necessarily DDR SDRAM per se, but only logical to take advantage of the natur interleave of memory systems.
You don't see video cards going with RDRAM. Or AMDs going RDRAM. Interesting, isn't it? 
3) All this talk about hyperthreading and stuff....so far...seems to be limited to the Xeon chips with mixed results. In some cases, they provide quite a substantial increase in performance (IF you can afford it), while on the other hand, it couldn't even consistantly repeat the same or similar numbers. So...what I'm trying to say is that the future and the practicality of HyperThreading remains to be seen.
4) With the Hammer series coming out soon, it'll be interesting. On that note: Intel's IA-64 sucked big time. Apparently they only sold about 2100+ chips, of which, 2000 of them went to IBM. So, retail or other OEM market, they only sold between 100-200. HA HA...and supposedly also, they've spent nearly $1B in developing it. Suckers.
P.S. DDR RAM's performance can be doubled with the introduction of dual channel memory. Why do you think that RDRAM has to be installed in pairs?
Downside to dual-channel DDR RAM - it TOO will have to be installed in pairs, limiting expandability.