Athlon XP is AMD's way of trying to convert between Intel and AMD CPU speeds. They are trying to hook into MS WinXP brandname and at the same time give a benchmark against the P4 chips.
Until Intel gets DDR/SD RAM mainboards there is no choice in the CPU (why are they are stopping production?). DDR is much better value than RAMBUS.
Interesting side note is the dropping share price of AMD. They are making the better chips but are in trouble as the share price has dropped to under $9 from over $25. Hope they don't go under in this war with Intel.