Actually, even from a performance perspective, network latency (i.e. there's a longer path) probably weighs against OpenDNS compared to the DNS caches of <whatever your ISP is>.
Reliability of the service is pretty crucial though, if you suffer lost DNS traffic then overall experience of any ISP is going to be rubbish (you can't do nuffink without DNS really). Decent DNS is going to make a difference for complex sites that drag content from lots of sources - like most things, faster is better, but reliability is king. I'd have thought if your ISP is dropping DNS en route to their own caches, then going off their network for it just isn't going to help.
I've personally never seen any evidence that VM's DNS caches are anything other than reliable on here, except for individual cases where specific things don't resolve and I expect that there's normally a transient upstream cause for those.
Anyway - the nice man at GRC built a tool to measure DNS latency - as previously posted, normal YMMM caveats apply etc.
http://www.cableforum.co.uk/board/12...l#post34924319