I don't think I would have engineered a new board and control stack just to get a web interface and a screen. Their last model (the i3 MK3S) has headers to accept a Pi Zero, and that seems like a good approach modulo the bugs, which would be worth fixing. (Apparently the bugs are, the Pi Zero isn't fast enough to emit gcode to the UART and record a video stream from a camera at the same time. I kind of doubt it, but that's what I'm told. The other problem is that the i3 has one power switch, so it can't keep the RPi on when the printer is powered off. This means a lot of people are corrupting their SD card, which is probably why they complain about the setup randomly breaking.)
I just want a USB serial port that accepts gcode. I have plenty of computers with much better screens (and SSL stacks) around for doing something more powerful ;)
That's fair, but then you've added an extra processor which adds a lot of cost. I don't want to tie up a full computer and the associated space just to run my printer. Many people don't have a spare computer they can dedicate to printing either.
From what I've heard, this is not reliable in the current implementations. If the computer goes to sleep, is under high load, or crashes this can result in a failed print. Of course you could build in more and more safeguards for this sort of thing (buffer the gcode, have some "emergency stop" movement which moves the head up and away from the print and decreases the temp of the hot end if there is a break in the stream of instructions) but this is a lot of additional effort when you could just as easily push all the gcode onto an SD card on the printer.
Write file, insert, pick job, walk away, done.
For very long prints, SD is my goto. No failures.
