The magic eraser is just the same as the magic wand, but the wans can adjust its tolerance levels so you have a more controled selection than the erasers.
for an alternate cutting method, and im not sure the GIMP has one too. Is the POLYGONAL LASSO tool. i use this as a secondary method for my cuts (and check out my results :P ),
i made tut long time ago on it. : StaticIllusion - Sasurai's, Simple Extracting method