I love the drive. The noise seems to be less if anything. My 4200 has a loud click it will do sometimes during heavy disk access. I could hear neither, though, during normal operation when installed in the notebook. the only time I ever noticed either making any noise was late at night if I had it on the couch with my head right beside the HD bay. I have heard some users speak of a constant whine, but mine doesn;t exhibit that.
As for improvements, a ton!
Boot time became significantly faster, all app loading times are very noticeably faster, and even gameplay (EQ and EQ2 are about all I play) became better oresumably due to the faster swap file.
When I got mine, they were much higher than they are now. If I remember right, I paid about $190 for it.
I have yet to find any con, except the reduced storage. OEM was 80GB and this one is only 60 of course. I took the old one and slapped it in an enclosure though.