Did you capo a 12 string for the R.E.M. tune? Sounds pretty good.
REM - You seem to have the 12 string sort of left, and the tambourine either center or just right of it. You might consider spreading the guitar out by cloning a copy and hard panning them, with one of them offset about 30 or 40 milliseconds. It may make the mix bigger, or it may just make it smeared and blurry, lol...hard to tell without hearing it. 12 strings are tricky. I'd really like to hear just another 6 string guitar opposite the 12 string.
Mayer - The acoustic sounds are pretty good man. Whatever you're hitting for percussion, I would definitely keep it static throughout the song. It's a bit distracting when it drops out.
Vocal gets kinda' pitchy in both tunes in places, but it's a nice voice. She sounds like she's really really laying back, though...some more energy in the vocals might help her pitch better, I don't know. It reminds me of how I sing when I'm trying not to wake up my wife while recording, lol.
Best to ya'll.
