Do you plan on running Virtual machines, do you plan on having tons of Apps open? If you have the extra cash it won't hurt to upgrade, but sometimes it isn't really needed.
With RAM, the more the merrier. More RAM will definitely give you a performance boost. Whether or not you'll take advantage of it given the tasks you described is a separate issue.
You should be fine with 2GB. It'll probably be a while before you notice it being bogged down by a lack of RAM, and by that stage, 4GB DIMMs will be dirt cheap