Finally, a laptop configuration from Apple that I won't need to add anything to for it to be useful to me. Of course, I'm not quite ready to upgrade from my Powerbook yet. The only question is to go with the default disk, or upgrade to the 7200 RPM disk.
Upgrade! I have had excellent experience with my Hitachi 7k60 drive since July-2003 and can wholeheartedly recommend fast hard drive for anyone. In fact, practically everyone using my laptop have been blown away with the speed, which is mainly because I have upgraded the slowest part in the system.
Do it! Your laptop is as fast as its hard drive. Faster CPU/GPU can do nothing if they're not fed with data from the relatively slow storage. Upgrade the storage and your system has more data to crunch...