IMHO, it's a no-brainer: SMP is DEFINITELY worth having. As
others have noted, your system will be APPRECIABLY more responsive
when you're multitasking. Want to encode MP3s while surfing or
playing games? Not a good idea with a single processor, but not
a problem with SMP...
And then there are the benefits for programs like Photoshop, that
actually know about multiple processors.
Now, if SMP was a lot more expensive, I could understand people
saying "not worth the cost". But, heck, you can buy the BX-based
stable-as-a-rock Tyan Tiger 100 dual motherboard for $100-150, not
much more than a comparable single processor board. The only other
additional cost is for the second processor (and you can run with
only a single processor, so you don't have to do the upgrade
right now, if you want to save money).
Kwad