A few issues aside the Retron 3 is a great little console. It is easy to power, offers flexible video options and has a controller that feels better than most clone systems. It also can maintain 2 different save states allowing players to use cheats and breaks without corrupting the original game file.
The Retron HD has a nice matte finish and comes with 2 NES compatible controllers (although I have found that the included Cadet controller is closer to the original NES design than the new clones). It accepts both NTSC and PAL game cartridges and also supports the RCA analog video and s-video output. There is a HDMI port and a micro USB port for power on the back. A switch allows you to select between a 4:3 or 16:9 aspect ratio.
This is a so called Nintendo-on-a-chip system, meaning that it uses a processor to simulate the NES hardware. This is not full software emulation like the Analogue Nt Mini and it can cause some minor problems with certain games (like colors being off or sound effects sounding slightly different to authentic hardware).
However, it is unlikely that many people who purchase this console will notice these issues. It is a good option for anyone looking for a cheap NES system. Just be aware that it doesn’t support the everdrive and that using a flash cart may not work as well as you would expect. I believe this is due to security protocols or just the fact that the hardware needs to be updated.