What it does is complicate things rather a lot. Continuations are an old, old
language feature. Unfortunately many folks doing language work didn't think about then when new language features were developed, so there are things which may not necessarily play well with continuations. They'll work, but may not be an optimal combination.
In the block exit case, finally clauses will be executed each block exit, which may be somewhat surprising, but not fundamentally an issue. The bigger issue is with things like local/temp/hpyothetical variables.