Well, up until about a month ago, I'd say that it's not worth it.
None of them cover congenital diseases, which are biggies (high $$ treatment) in boxers. For that reason, I never got it for either of my 2. The kinds of things that would really hurt me financially, wouldn't be covered, so I decided that I would be better off putting money away for them each month in case of an emergency. That way, I decide what kind of treatment is covered.

You should do that anyway because most (except Banfield, I think) reimburse you for your expenses rather than covering up front.
However, most of them cover accidents - accidental ingestion, dog hit by a car, etc. I might be $1200 richer if I'd had Conner insured when he swallowed some bones whole and got a bowel obstruction last month.
My gut still says, no, but I'm looking further into it.