Trouble with SSD/HDD in Macbook Pro Mid 2009
Is your MacBook Pro the MacBook Pro (15-inch, 2.53GHz, Mid 2009) model?  That model of MBP had a known issue where it would constantly beach-ball with non Apple drives.  There was a firmware update available but that hasn't fixed all units.

From personal (and professional) experience I've found upgrading to Mac OS X Snow Leopard 10.6 fixed about 50% of the time, all other units had to have an official Apple drive fitted to fix the issue.

Basically your only options are to upgrade to Snow Leopard (I'm unsure of whether Lion includes the relevant firmware updates) or complain to Apple so much that they give you a replacement unit.  Ugh.