I too use it extenstively, especially if I want to edit as well as view one or more shared Actions being called by the test script I currently have open in QTP's IDE. But on this point: if you edit a shared Action called by the script open in the QTP IDE, you need to close and re-open the script in QTP to see the changes made to the shared Action. But that "round trip" (close and reopen) is quite fast.
I've been extensively using it lately. Esp. for tests with calls to shared/re-usable actions. Haven't faced any issues yet. Biggest benefit as people have noted - ability to open & edit multiple scripts at the same time.
The only con, I have noticed is absence of intellisense. But having spent considerable time programing QTP, this is quite negligible issue.