sensible upgrades depends on what they have right now
QFT

Some of us have first gen dual cores and have been happily sitting out the quad core race waiting for something better than a 10% improvement. Simply realize that Yorktown brought 15% or so clock for clock and Nehalem might improve that by 20% or more. That's a lot bigger jump for those who skipped the Yorkies. So yes if you bought a system in 2008, you shouldn't want to get a new Nehalem. It's nothing more than a stepup. But if you have something older, Nehalem should finally entice you to build something new.

2nd thing to remember is that the bulk of Nehalems won't be out till next year. But for those of us who have put off upgrades waiting, we won't wait till then