Its not a perfect resource but it's also, in my experience, never been wrong...it has choked out a couple times with
no info. I can live with that. The best way to test it is at home with what you know, right? It's just nice to have in a pinch.
I use it quite a bit...and then follow up when I'm in front of my computer at home.
Besides...no info can leave you kicking yourself sometimes..I like to have a general idea, and then use google/ismacs to back it up.