Bigger – certainly. This will allow you to install more programs, and store more documents on the card (of course, you could also rig up something with an external hard drive). Just remember to increase the size of your root partition (the default for most of the images is less than 2 GB to fit on a 2 GB card).
Be careful about buying faster drives at the moment: there are currently problems with Class 10 SDHC cards that are apparently caused by a bug in Broadcom's loader. See: http://elinux.org/RPi_Verified.....s#SD_cards
Check out cool stuff I'm doing, e.g my PIC Programmer for the Raspberry Pi: http://www.techmeology.co.uk/rpipic/