Some people have promoted GridCoin and PrimeCoin as coins that potentially have better features than BitCoin. However, I don't see how this kind of feature will lead to massively increased adoption. Sure, you might feel good about helping people when you mine GridCoin, but the fact that your processor cycles are going somewhere useful doesn't actually positively affect the ease of adoption of the coin itself, with regards to its usefulness as a currency.

Plus, with GridCoin, there's the added security headache that comes from a possible breach of the computers that manage the supercomputing work (I'm not an expert, so I may be mistaken here). If GridCoins were $1000 a piece, people would be attacking that infrastructure like crazy.