Sorry for the delayed response. I'd been monitoring this question to see if other responded.
I've used ViewPoint quite a bit. I really only use it for website access and less for the duration. I've found bandwidth utilization to be useful as well.
Website access can be confusing. What I've discovered is that when accessing a main site, subsequent sites are accessed, creating confusion of where they were actually visiting. However, looking at trends over time the real websites will eventually emerge.
What I have found since is my clients not only want to know WHERE their clients go, but CONTROL where they go. The sonicwall doesn't do whitelists very well. We've opted to utilize CCProxy. We require the users to login when launching IE. CCProxy syncs with active directory, so we get a good account of who goes where. CCProxy does a little better job of reporting website access.
Anyway, those are my 2 cents worth.