OpenGL is hit or miss for me so far. Some games seemed to run great with it - I booted up Wild Arms 2 briefly and it worked wonderfully. It's the first time I've ever gotten a good FPS in that game - it looks great and playable.
FF7, meanwhile, is a hot mess. With OGL enabled I'm getting tons of video corruption all over the place, some cursors are missing, movies are corrupting during playback.
The FF7 battle screen is also a COMPLETE mess, and is unplayable, due to severe mangling of the display - half of it is squashed into the top of the screen, while a duplicate image exists on the bottom half. Also, the dissolve transition into battles in FF7 does not work, and causes MASSIVE slowdown and FPS loss - according to the FPS counter I hit about 10fps during a dissolve.
It appears that the "limit screen size" parameter does not always set correctly when enabled during a game that's running. Turning it on or off does not always immediately set/remove the black bars, and if it does, it just chops off part of the screen rather than resetting and redrawing the screen correctly. I had to turn my phone to portrait orientation then back to landscape before it properly reset and redrew the screen correctly.
OpenGL is also seriously messing with MDEC video playback when it's enabled. The FF7 intro video had corruption and other playback problems, mostly double images in the portions of the screen that were supposed to be blacked out due to "Original Screen Size" being enabled.
It also appears that displaying the FPS counter impacts the framerate - games seemed to run markedly smoother with it turned off.
Would it be possible to get some kind of OpenGL "low resolution mode", where it still renders the game to the OpenGL, but it renders it in its native resolution, rather than a high res version? This might help improve speed while offering an "authentic" experience for games that get corrupted or distorted in various ways by having their resolution increased.