You are correct, but the number of blockers is getting smaller. I sympathize with your situation, boto is a pretty big blocker (PIL was too until I switched to Pillow) and it impacts several of my projects, but thankfully I can work on porting my code to 3.x with six https://pypi.python.org/pypi/six and still deploy on 2.7 until boto gets there.
and Twisted seems to be making good progress:
http://twistedmatrix.com/trac/milestone/Python-3.x