You will regret it. If you are the kind of computer user who could buy a Dell because a MBP didn't have the latest specs, then you will regret your purchase.
Macs are great if you care about the software, and what the software enables you to do - and if you believe Mac OS X and Mac software enables you to do more or better than Windows XP or Unix. Yes, I think they have great industrial design, but the physical components and color are really just a shell for software. And if you believe Mac OS X is superior, it doesn't matter what the specs are, there is no way you will buy a Dell.
However, if the shell - the components, and specs, and numbers - is what is important - then it is Penryn or bust.
For all the people that are waiting I've never hear anyone say "I do X with my computer and can't do that with the current MBPs, but I could with Penryn MBPs so I am waiting." For those people, they should wait. And for those that care more about the specs than the wait is also necessary.
But for those of us who care about the product we make with our computers, then there is no wait. You buy when you have to buy, and you keep on creating.