Re: IP Exclusion
There probably isn't much benefit if, as you say, the persons IP address is changing regularly. Other than that, there are benefits. The main benefits would be the ability to block your own office usage skewing results (if staff use the site a lot). Also, if you have staff who work from home, you could block their IP.
You might also know the IP address of competitors or partners, who you don't want skewing data.
So, several benefits, but perhaps not so much if they are on a dynamic IP which changes each time they connect.