I would buy. People will always tell you to wait, but if you wait long enough, you will get a 64 core core 20 duo with 20 GHz and 1 billion gigabytes of RAM running Mac OS 12, but the longer wait, the longer you go without a Mac! Don't worry about updates, because if you do, you will never get around to buying a machine.
Sure, I could have waited for the Santa Rosa iMacs coming up, but if I did, I would still be on my crap Gateway PC that I cannot stand, so I bought my computer when it was the best out there. It is still the top of the line, but it is not about having the top of the line, it is about having a great computer to use all the time. If you want the top of the line (all the time) anyway, you shouldn't be buying a Mac anyway. Do yourself a favor and get the MacBook you want
I bought an iPod photo a few months before the iPod video came out, and I am glad I did, because if I waited, I would have gone those few months without an iPod. It will be worth it because either way in a couple of years you will buy another computer, right? Hope that helps.