I got the Retroid Pocket 2+ yesterday and it's brilliant for Dreamcast.
It currently isn't brilliant for:
PC game streaming. The wifi is good, but the lack of L3 and R3 kills the games I enjoy the most on PC.
Gamecube/Wii: So far, Wario World is the only game I'm getting 100% frames on. Double Dash and Animal Crossing are playable. Sunshine isn't. Metroid Prime... might be. So far, I'm not really seeing a lot of improvement by lowering internal resolution on games. A game that stutters at 1x resolution seems to also stutter at .3x resolution.
PS2: I haven't played around with AetherSX2 that much, but so far everything is too slow. And again, no L3/R3.
Mine also arrived with noticeable light bleed in dark scenes, which can apparently be addressed by loosening some of the internal screws. I haven't opened it up yet to try.
Still. 100 bucks.
Edit: Paper Mario GC also looks like it's working at full speed with some visual glitches when new scenes are being loaded. I can't predict how a game will run. The busy 2.5d in Paper Mario is no problem while it chokes on the N64-port graphics in Animal Crossing.
I'm posting this edit on my retroid. My touchscreen is working fine, while others have trouble. Maybe the QA crapshoot has something to do with the low price.
My performance impressions are all with Google Play Services installed and running.