Professional reviews indicate that it is fast, user reviews indicate there are problems but bare in mind that people tend to leave reviews more often if they have problems than if they do not. It is pretty much the same story with every sand force SSD on market (except Intel). If you value reliability the most then Intel followed by Samsung then a Marwell based drive like the Crucial M4 is the way to go.
I have an M4 in my work PC and it's great - I've had no issues with it. I'm just looking at all available options - I like my Intel drive but it has not been proven to be the most reliable - it is fast, but definitely not reliable.