We use Voloviewer here and it works great. I couldn't even begin to count how many seats we have. I've heard evil rumors that AuroDesk is going to drop it soon in favor of the .dwf viewer. Tim Riley suggested paying for composer but, why bother with that when you can get a free .dwg writer and they can then view them with Internet Explorer. That's the whole purpose behind this .dwf craze..
Funny thing, at least in 2K4, did you know you can't open a .dwf with AutoCad?? At least I haven't seen a way.
I had thought about getting one of my techs a copy of AutoCad LT the other day, until I saw the latest price.. WOW!!