I'm definitely not expecting any significant, perhaps even noticeable, performance bump from the 2.6. Simply put, it's about resale: When there is some new "latest and greatest" that I just can't live without, I'll be putting this one on ebay. At that point, I'll want the beefiest specs possible to be most competitive with any other MBP's that happen to be listed at that moment. In the meantime, I'll have as good a MacBook Pro as money can buy.
I'm just generally in favor of buying my Macs "loaded", and I've never regretted having done so. When is the last time you ever heard somebody say, for example, "I wish I had LESS RAM", or "my computer is too fast" or "I replacing my hard drive with something smaller"? For the most part if you can afford it, within reason of course, go for it. You won't regret it.
As far as the waiting game, forget it. You'll see Penryns delivering in February. They'll be a nice little performance bump. In the Spring/Summer you'll see the new chip sets and perhaps a real update of the whole MBP line. Let them work the wrinkles out of that one and it will be the one to get. But do you want to wait until July for your new laptop? The 2.6 MBP I get next week will serve me well for the next year.