CS3 is fine but very out of date now. I would recommend spending a little more and investing in CS5... even if you need to wait a bit longer. Alternatively, find out from Adobe how much extra you would have to pay to upgrade to CS5 from CS3 at a later date. Of course, there's always Photoshop Elements 9 if cost is an issue. It really depends on what kind of editing you want to do. Most of the basic editing these days can be done in Elements. Photoshop is a deeper dive with high end editing abilities.
Go onto adobe.com and they have the CS5 Creative Suite available for trial for 30 days, that way you can test it out for a month and see if that's how you want to spend your money..
Thanks!!!