Open Stack

Hey -- I've run a number of OpenStack clouds from multiple vendors for 
several years, now.  But I've *never* done an upgrade.  I've read some 
of the docs, but they don't really make it clear (at least, the ones 
I've thus-far found):
* If going from Juno to something pretty recent is even feasible
* If I have to do intermediate steps along the way
* How likely it is to "just work:" complexity, common issues, etc.

The fact that there's a clearly codified fallback procedure, while an 
inherently good thing to have, does concern me some.

Any insights would be much appreciated.

Thanks!

-Ken