Let's face it, the iPad3 is all about the screen. If you want the screen then get the 3, if you're not fussed then the 2 is a better bet.
As for whether you want the screen, it's all down to what you do. If you're primarily using apps then, whilst the screen is nice, most apps have been optimised to work fine on the iPad2 screen too so everything is large enough to read comfortably, the 3 just looks a bit "nicer".
If, however, you're doing a lot of reading, either of websites or books or magazines, then the screen is worth every penny. You can read more easily without zooming or panning as much, it's less fatiguing on the eyes when reading small type and web-browsing in portrait mode without zooming at all becomes easy when, on many sites, it was virtually impossible before.