I’ve been running with the new hard drive for 5 days now and can add a little more info to the experience.

• Battery life has not changed, which is very good news. I figured that since the drive spins a little faster (5400rpm instead of 4200rpm) it would consume more power. It may, but it isn’t noticeable to me.
• Heat seems to be the same. As with battery life, I expected the faster drive to generate more heat, but it seems to be the same. Another plus.
• Noise. It is a little louder than the stock Hitachi 80GB that came stock with my PowerBook. Not so much when seeking, but there is a constant “whir” that you can hear if the room is quiet enough. I’d never notice it at work or any room that has other sounds going on, but I can hear it when there is no other noise.
• Speed. Everything feels a little faster, but it’s not an in-your-face kind of speed increase. It’s a pretty subtle increase for day to day web browsing and email. When I really notice is when I do heavier lifting like iPhoto or Photoshop Elements. There is no doubt it is faster when dealing with large files. Even the larger videos I watch with iTunes are a little smoother now. I have had problems playing HD content without it getting a little choppy in the past but it seems to hold up better with the faster drive.

Overall I’m still very happy with the upgrade and am glad I did it. I would definitely recommend it to anyone that is even slightly technical and not afraid to open a computer. There are some great guides online for replacing the hard drive, so print them out, including the screw guide, and go for it. I knew going in that a move from 4200rpm to 5400rpm would only be a slight increase in speed, but I couldn’t find a big enough 7200rpm drive. I think the biggest one I found was 100GB. Not enough of a space increase for me to open the case.