I've never heard of them, but the page looks impressive. The only concern about phpBB is that the code quality is really weak (strictly imo). I hope forumer keeps up with updates and security fixes.
Otherwise looking good.
Btw, it doesn't take much to host your own forum. PHP webspace with a MySQL database can be purchased from 1-2 bucks per month. Then there is a ton of boards to select from, for example (my current favorite)
vanilla. And that is totally adfree - for forever.
Hope that helps,
Till