You've hit the nail on the head there. If you need it now then buy it. There will always be somehting better just around the corner, but sooner or later you will have to bite the bullet and buy. I actually think now is as good a time as a few months ago for purchasing a MB(P). Sure, C2D's are almost here, but who knows when they'll be in the portables - and more to the point, how many people out there will actually use them to gain full advantage? Those who are seriously into video editing will probably opt for a more powerful desktop than a portable, and outside of some hefty video/audio engineering, i'd be very curious to see if the average user sees a notable difference between the CD and C2D.
Of course there are always people out there who want the latest and greatest technology just because it's there - thats a perfectly good reason to wait a few weeks for a new release. If you need one though, I'd recommend you don't get caught up in what is arond the corner, but buy what will serve you best now.
/end rant! 🙂