I don't use them personally and we have very few customers at my current job that will request them.

I used to work for an anti-spam company and the request would come in from time to time to have SPF checking built into our appliances. As developers, we did see the benefit of it. But at the time, there was the SPF vs SenderID vs Domain Keys battle going on. Who would win out?

As it appears years later, no one really did.

The problem with the technology is adoption rates. Unfortunately, many of these technologies are not being adopted by the masses. I'm not saying its hurting you by having these in place, but it also might not be doing as much good as you think that it is.

LightEdge Solutions (http://www.lightedge.com/) was actually the first hosting provider to have full integration with Broadsoft on the UC front. Very reasonable prices for Exchange, OCS + a hosted PBX seat all tied together.