Getting the opteron now would be a HUGE investment considering you would have to buy the chip at +$700 (the good one not the crippled one), registered ddr memory and a motherboard. Hell, I think I spent $700 for my total system last time I upgraded (w/case, powersupply, pci cards, hd's blah blah blah).
How can this be considered mainstream at the prices and there is virtually no software support, maybe in a couple years there will be. Would be usefull to someone running a huge server with 64bit Apache but not as a gamer or websurfer now.
Aces hardware has a good comparison article up of the different FX's and the P4EE.
http://www.aceshardware.com/read.jsp?id=60000253