I would like to detail my early experiences with porting my Ruby 1.8 and Rubygame 2.5 based project to Ruby 1.9 and Rubygame 2.6.
It went quite smoothly - just had to install the new gems for Ruby 1.9, and that was it - so good job guys! However a few points:
I store paths as Pathname objects. So I'll do 'ROOTDIR + "blah.ttf" which gives a Pathname object, which when 'to_s'ed, gives '/root/dir/to/game/blah.ttf'. Rubygame::TTF.new and Rubygame::Surface.load both require the Pathname to be explicitly be 'to_s'ed now. They did not before.... Still it's not a problem, my tests picked up the problems and I fixed it in a matter of seconds. Just something to keep in mind.
It is a bit slower. Disabling vsync and the Rubygame::Clock, I ran a demo at a low resolution, and ruby 1.8 with Rubygame 2.5 achieved 150fps, while ruby 1.9 with Rubygame 2.6 achieved 140fps. So Rubygame 2.6 is a bit slower, however the added convenience of Ruby 1.9 means I'm going to keep using it.
However, everything else WORKS! So great effort, and keep up the good work!