I'll write two posts.

Now that 1.9.1 is released, hopefully people will start porting to it, 
and 1.8 can remain stable. For the people who still need all their old 
gems to work, there should be a stable version -- apparently, 1.8.7 
broke a lot of things.

On top of which, if 1.8.8 is an easier upgrade than 1.9, people won't be 
as encouraged to port to 1.9.