If you're into that sort of thing, I'd definitely invest in one! I have one and its tons easier to use photoshop with, and much more gentle on the hand strain, lol. Its great for using the brushes and all that sort of stuff and very precise, I love my Wacom to bits!
If its a bit too expensive, try getting a second hand one, other companies make tablets, but the quality difference between another and a Wacom is huge, so its best to save your money for the real deal, that way you know you aren't going to have driver issues and there is a reliable website to help back you up.
www.wacom.com