Much as I've loved ack, I'd be all in favor of a replacement that was really significantly better.

That said, the readme there lists five reasons why Silver Searcher is better than ack. Two of them are nonsense (who cares what language it's written in, or same-order-of-magnitude differences in how big the executables are?), two sound like they would be pretty trivial changes to ack, and the last is a significant speed improvement. But then you read further down the readme, and it says the current development state is somewhere between "Runs" and "Behaves correctly". Isn't it kind of premature to be bragging about how fast you are before your code actually behaves correctly?

Also, it makes me wonder how much of the speed increase is based on the easy changes filtering out more files...