Do real estate websites provide enough information to make good purchase or rent decisions?

Use it to eliminate some properties, then, go look.

If it were me I would not make a decision like that without seeing the property. Estate agents (as we call them) are well known for exaggerating a description to get sales!

I think it depends on the site. A lot of condo sites post data, price increases, and things like that. I've found less info on others for houses though. I still believe that nothing takes the place of doing your own research, even if there's a lot of information available.