Yep, I'm thinking I'll definitely be buying it. Just not having to stop and restart the entire game and get to the same position I was in a minute before just because I wanted to override a method in some class is incredibly good. Every time I have to stop and restart the game I'm wasting about a minute. Now I can do everything just by editing it. Combined with my newfangled XML-file-watching and texture file watching stuff it means I literally fired up the game yesterday... and left it running all afternoon while I continued to code it. Just awesome.
Not sure that Xrebel is much use to me though