Forcing GPU rendering for 2D is *Awesome*
I can't believe I didn't know about this before. Basically, in the developer options, there is a checkbox for "force GPU rendering for 2D drawing".
With this enabled my older phones and tablets are SO smooth now. It is a night and day difference. So far I have not noticed any difference in battery life (though I am sure it must affect battery somehow).
Enable developer mode by going to the "About" menu and tapping the Build number till it appears (I think it is 7 times, but tapping more than that won't matter). After that a developer menu will appear in your settings.
Tried this on 2 tablets and an older phone so far and it has worked great. One of the tablets was an very low end Azpen tablet (paid $40 for it brand new to give you an idea), and it even worked well on that.