SMP for 98% of the home users out there is OVERKILL.
Come on now people, admit it.  How many people do you know that use computers are barely literate with the machines, let alone anything with the internet related.  Most of the computer users I know know little to nothing about their hardware and know even less about how the internet work.  All they know is: turn machine on, click on dialup shortcut, click on email shortcut, click on browswer shortcut.
For these people, SMP really means nothing.  Unfortunately, that's over 90%+ of the users who use PCs for their "day to day" use.  Nothing wrong with it, I'm not bashing them, but I want to point out that the simplest tasks don't need SMP.
HOWEVER, for the <1% of the users out in world, WE are ones who know more is better when it comes to SMP.  I have an SMP rig at home, but its my server and not my gaming box (2x P3-550s).  I cannot wait until AMD gets full gear into SMP so that Intel can fight against them for the workstation/server market.  More choices for us is a good thing because no single company can screw us on the prices for the hardware.
I believe that SMT+SMP is the real key to getting much more speed for less money.  SMT is essentially two processors on the same die (from Intel anyways).  Putting two processors on the same die is just like having SMP, but without the added space.  So, put two SMT processors on one board and four processors for the price of two!  Woohoo!  Unfortunately, its an Intel only thing and its not "out" yet (sampling).  SMT has more of a chance of being commonplace (ihmo) than SMP because of cost.
Either way, I want a dual AMD rig.  But I'd want a SMP+SMT AMD rig.  That'll be some bragging rights!
vash