I had some of them driver crash windows pop ups right at the start, since then Windows has done big updates, I installed all the latest drivers, updated the firmware, etc. Since then I have been playing through Rayman Origins on the device, played for several hours without any issues (no crashes, no stutters). I would very much recommend this game, it plays really well on the device (both in terms of performance and controls, and the game is a masterpiece in terms of visuals, audio, gameplay). I am still slightly worried about whether my unit has any problems after the initial GPU crashes, but I'm hoping to just keep hammering away and see if anything comes up.
With regards to the deep sleep, I feel like I've had it happen once. But then it seemed to do it yesterday, so I pushed the power button again, and just as I did in the screen came on, and then went off again (presumably it took a while to kick in, then received my second push and went off again). I pressed a third time and it came on, so I need to monitor it/investigate a bit more.
One thing I have fallen foul of a couple of times is starting a big Steam download, leaving the devices plugged in via USB to a USB hub (to charge), and then the system sleeping and not finishing the download. Have just manually been changing the power configuration temporarily whilst download for the time being. I would use the proper charging cable but it came with an EU plug and I'm in the UK, so I need to buy a plug converter.