Hm, this might just convince me to reinstall my Momentus XT (SD 26) in my MBP (early 2010, 2.66GHz Core2Duo, 8GB RAM, running 64-bit kernel).
I removed it after a couple months' trial, due to dismal battery life and oddities with hibernation. The replacement, a highly-regarded 7200 RPM Hitachi Travelstar, is okay but I get considerably more beachballs, and the battery life is better but still more severely impacted vs. the stock drive.
I'll be watching this thread closely for more details about stability, hibernation and battery life.
If good reports continue to come, then what I might do when Lion drops is back this drive up, swap the Momentus XT back in, restore, verify all's well, then do the Lion upgrade on that drive. That preserves my current drive and Snow Leopard setup...