I own a 10k RPM drive. I love it. It was worth evrey penny..
I recently switched all my valve games to the 7200 RPM drive and it was alot slower.
I reccomend them. I might be selling mine soon as the 150 gb does not give me enough space. But I still highley reccomend it.
Its not lound at all. I dont notice it at all. also I would like to say my WD 200 GB runs hotter then it. But I think it varies.
Things that go faster:
Games, OS loading, Photoshop, and progam responsiveness.
I reccomend it.