Weird possible hard drive issue...

Just replaced my 120 GB drive with a 640 GB drive. All went well with the install. I installed Snow Leopard first on the drive via external enclosure, then installed the drive and migrated my user profile via Migration Assistant. All updates are current and I even reset the PRAM.

I get some sluggishness sometimes when web browsing. Seems like the system stutters a bit, I get the spinny pinwheel, then all is fine. There is also a bit of a lag in MS Word, or typing emails.

Do you guys think this is a problem with the drive?

2.2 MBP w/2 GB ram