754 - Is already "end of life", has been for some months now.
939 - Will be "end of life" by mid 2007
Main reasons AM2 -
Supports DDR2,3 and FB-DIMMs.
Ability to have multiple CPUs (can't be done 939)
AM2 was actually delayed for about 8-10 weeks until the faster DDR2 memory came onstream.
Personaly I'm happy, by the time I get my new whatever rig in Q1 2007 I will have got 18 months out of my 939 setup.
By Q1 2007 I will have the choice of -
1) Conroe - Lower cost than the projected Sept 2006 avail to "Joe Public".
2) 2 x AM2 K8 rev g on a "Torrenza"
3) AM2 K8L on a "Torrenza"
Way I look at it -
a) IF I can get two rev g AM2's for the approx same cost as a single Conroe, for me 4 cores are better than 2.
b) IF the K8L fulfills its promise and is priced similarly to the Conroe, then I may go for a single K8L, and save the second socket for a later upgrade.
c) If neither (a) or (b) is feasible, then it's a Conroe.