I am planning to make two versions of most my games anyway. The low end phones should not have the graphics for the high end phones in their APK anyway. They would just be mad about having to spend most their phones memory on something that will make the game unplayable on their device anyway.
And if you browse the Android market with a 2.1 device or lower, you can make sure they will only see the low end version of the app, and I am pretty sure you can make it so the market does not show the low end version to high end users.
I have begun playing around with GLES2 a bit, but for now I am still only using GLES1. Too often have upgrades to the engine cost me a few weeks to deal with, making my code fit with the changes. It sounds like the changes from the newest versions of GLES1 to GLES2 are quite small, and I have not met any problems so far, but probably only because I have not really been using GLES2 much.