In some light it could be seen as "bad," at least as currently structured in this country: we basically allow people to withhold tax money and instead direct the money as they see fit, which has an anti-democratic implications -- in effect it as though we went to the richest Americans and said "why don't you decide how a substantial chunk of tax dollars are spent rather than Congress?" Beyond the more philosophical aspects, having been in the sausage factory for a bit, and having read about others, I think it is very easy for charities to just happen to serve their mission in a way that just happens to be more beneficial for their patrons (even if they could put superficially convincing numbers on it to prove they're highly "effective").

But I suppose I would say it's neutral; it could be good or bad depending on various characteristics of the charity itself.