The catch is that every single part of the system is some kind of janky hack job.
I have one of their GameShell devices. The things on the sides that look like knob controls are actually clasps to hold the thing together. Took me a week just to figure out how to SSH into the thing. Screen resolution and picture quality is really bad. All of the buttons feel awful, with a lot of latency on presses. WiFi just craps out whenever you breath a little hard on it. Performance is about like trying to run modern Linux on a 15 year old PC. Lots of fantasy consoles preloaded, but the screen, performance, and buttons all add up to making it a terrible experience, and there are only one or two good games for each, anyway. Lots of very poorly implemented PyGame games that have such neat features as "no way to kill the process from within the app to return to the main menu" and none of them are actually even close to good ideas, say nothing about complete or decent games.
Iffy software support. If you look at the Clockwork Pi forums there's a lot of complaints about a lack of updates. There's some community support for alternate/upgraded software, but the user base is small enough that we're talking "download a ZIP file from a rando who says it works for him". It's DIY but also "figure it out yourself".
I bought both a DevTerm a04 and DevTerm r01. The catch is software support (if this is going to be similar to other clockwork pi products using the same modules), which is entirely left up to the community. With that said, the community mostly supports the a06 and RPi CMs. Their hardware is actually quite good, as is customer support for that hardware. Just be advised that anything other than Rpi and a06 are going to be very rough on the software side of the house.
Too good to be true. What's the catch?