I setup fax.com during a network upgrade for an attorney client several years ago and they have been using without any problems. As a matter of fact they love it.

We were just talking about it a few months ago and the owner said she would never go back.

Bear in mind, they have some killer 20ppm ScanSnap scanners [Link: buyfcpa.com] installed on every PC in the office so its very convenient for them.

They also have a nice array of NAS with structured file directory sharing. Their "practice" is that every piece of paper that walks in the door (mail, receipts, client paperwork, etc) immediately gets run through the scanner and archived on the NAS. Once on the network, they can fax, email, print or whatever they need. The paper(s) then go into a bankers box, sorted by date only, and off to storage when full. They basically have zero paper in the office.

I would like to implement something like that myself. It seems to work very nice.