I read an in-depth review of notebook HDs a while back. The results of their tests was that the difference between a 4200 and 5400 was huge and made more improvements to the system than anything else they did (mega RAM, faster CPU, etc). However, the difference between the 5400 and 7200 RPM drives was very small, and doubling the RAM from 512 to 1024 made a much better improvement overall. If I remember correctly, the jump in battery useage was also greater than the improvement in performance.
-- Ah sh*t! sys64738 --