I agree, their pre-signup information is lacking. No screenshots, no pricing info, no "what the hell is it", just a signup form.

I signed up recently after seeing repeated recommendations on HN however and its actually very good and I've started using it quite a bit already. I'm not sure that I could explain it sufficiently here so I'll just say try signing up and give it a go (it didn't ask me to even confirm my email address so getting started was pretty quick).