Other than invalid complaints (did not meet the requirements for a complaint, was not a copyright complaint, etc) we have never had an abusive DMCA notice -- 100% of our notices (and we usually get a couple per day) have been valid.
We don't have the issue with our host being able to unplug us that easily (we manage our own network) but we do have the issue of liability, which the DMCA solves for providers like us.
Also -- I'd definitely be interested in the cases you're referring to, where false DMCA claims have resulted in major damages.