Primarily I want searching, sorting, and filtering, and the ability to quickly get sums/means of selected cells would be nice (although not really that necessary). I've been using Modern CSV for a while now (after discovering it on HackerNews last year sometime), and it's mostly very good (good enough that I don't regret the purchase price), but it has some stability issues and the documentation is severely lacking. But the main thing is that it's not quite good enough for me to not have to at least occasionally break out excel.