I love my terrier mix to death but I'd think twice about getting another one. I still think a german shepherd mix is probably the best. They're incredibly smart, so they're easy to train, and if you get a mix you can bring down the size a bit.
Based on what you've said about terriers, I am rethinking my next choice of dog. I love the look and size of terriers, they're cute little fuckers, but I don't know if I could deal with the problems.
I will probably stick with herding dogs, although there are a couple of sporting breeds I like, too.