bbrosemer, I think what some of the comments here are trying to point out is that if you sell your current MBP on eBay and buy a new Merom-equpped one, the price difference is likely to be less than the cost of the new logic board even assuming that the internal layout isn't so different that the swap is feasable at all. And that method, while it involves some hassle, doesn't involve having to procure a Merom-MBP logic board, you don't have to take anything apart, it doesn't void any warranty, and you get a brand-new, under-warranty computer at the end.
Now, if you're thinking farther down the line, when the current MBPs have dropped significantly in value (though at least historically, Apple laptops have held their resale value EXTRORDINARILY well), you're out of warranty, and the Merom-equipped motherboards available are running much faster than first-gen one is likely to, then maybe it'd be worth a shot. But that requires a lot of things to line up, the most unlikely of which is Apple not significantly revising the internal layout in the process.