If all you want is to see logging output, you can always print directly
to System/out so that it appears in the `lein repl` console. The fact
that fireplace captures *out* but not System/out is quite handy.
If you want to achieve asynchronicity, that is a longer discussion. You
may want to check out vim-redl by David Greenberg, as the provided repl
will return control to Vim after a timeout.
Otherwise, you can do what I do and create a little eval wrapper that
wraps expressions in a future, and swaps the future into an atom of
async expressions that you can query later.
HTH!
guns