[kbenson]

Well, that's half of the downside presented, the other half is that it's split be server/client connections. I assume this was done because it simplifies the tracking of the next stream identifier, because you can just keep a counter and increment, rather than a table of used streams to check a new random identifier against?

[bagder]

Correct, something that was used already in SPDY and proved to be very handy and convenient so it was kept in HTTP/2.