They contacted me 2 weeks ago and I also noticed the past payment history problems.  It was sort of a mixed bag: some good/some bad posts.  not particularly a good sign.  The person who contacted me wrote back and said they have been in business since 1984 (although he might have written 1994 -- sorry, I don't recall at the moment).  I decided to give them a chance, but explained they are on "credit watch" (I also have a "credit hold" in our system) and if they did not pay my invoice IMMEDIATELY, I'd stop work and start the collections process (which ends up in a lawsuit -- which I do -- all too frequently.  I even win!)

It's too early to tell if they're going to be reliable.  I'll post if they don't pay.