I wished I had gotten this one when I upgraded the HDD of my MBP, looks pretty good.
But it was just out then, and on back-order everywhere, and I got a WD Scorpio Black for a good price, so that's fine.
As for speed increase - did you replace a 5400 HDD with it (MBP), and was that harddrive wiped clean on a regular basis ?
Going from a 5400 to a 7200 HDD , in combination with using a fresh system clone, can do wonders in a laptop.
OSX DOES fragment drives !

As for using it in a MacPro - I only some reviews, but it seems the Momentum XT is still behind in speed compared to even the 'old' Velociraptor (not Raptor), so it might not be such a good option for desktop drives.
I believe it's about as fast as a current 1TB Caviar Black, which isn't too shabby.
Have you tried it in a Raid0 ? I'm wondering if the NAND still works then.