Yes, there is a noticable difference. 7200 will give you 1.33x performance without NCQ, and that number should increase with NCQ (which is defualt on a lot of SATA drive, so far as I know). I'd say its worth it.
As for battery life, there will be more force applied to the disc platters for spin-up/spin-down, and only slightly more force while spinning due to increased friction... But the friciton is negligable to begin with. I'd say the effect on battery life is 5-10 mintues, tops, IMO.
What are you suing your laptop for?