Of course, one of the really big problems that a lot of folks had with this episode is that the premise is basically a retread of "Lady Bouvier's Lover", except this time, Grampa falls in love with Marge's sister instead of Marge's mother. When I read about this episode (I haven't seen it yet, but it's in my collection), I remember thinking to myself "Did they forget that they've already done this or what?" I have no doubt that the episode has enough in it to set it apart from its predecessor, but still, the writers should have known that fans would make the comparison.
This seems to be a common thread in recent episodes - take ideas from older episodes and just change them a bit. For instance, the first time Homer went to India in "Homer and Apu", it was to get Apu his job back at the Kwik-E-Mart. The second time Homer went to India in "Kiss Kiss Bang Bangalore", it was because his job at the power plant got outsourced. Doesn't change the fact that he's already been to India, though.