Would installing the pre-built PCB require any sort of soldering, or is it as easy as dropping the new PCB in and reconnecting a few ribbon cables?
No, no soldering would be required - I'd send you a fully-assembled drop-in replacement board. You'd need to have a 7/32" thin-wall nut driver to open up your M, of course, but I assume everybody on these forums already has one of those... (Otherwise you wouldn't be able to open the case up to clean the thing, and you guys all keep your Ms clean. Right?)
The only gotcha is that the older Ms - the 1390120 and 1390131 for example - have one 16-pin connector and one 8-pin connector. Some of the 1391401s that I have contain the same connectors, but some of them have a 16-pin and a 12-pin - in later models, I think, they merged the 4-pin LED cable into the 8-pin keyboard matrix cable.
So just to be safe, I would suggest opening up your M and checking the ribbon cables to see which board you'd need.
how quickly does the microcontroller scan for keypresses? we've run into usb keyboards (like the das iii) that apparently don't do a very good job of it, resulting in typos that are the keyboard's fault.
I'm actually not entirely sure exactly how many hundreds of full scans per second the code does in realtime, but the answer is "hundreds of times per second". I've never gotten a typo that wasn't actually my fingers hitting the keys in the wrong order with this firmware.
EDIT: A somewhat rough test, using
PowerTOP, shows that my firmware appears to be waking up the USB controller roughly 150 times per second. I send a USB report once every full scan (which is a bug, but turns out to be useful in this case), so I think my sampling rate is roughly 2.5x that of the Das Keyboard 3.
I
have, however, had some issues with certain systems and my board's firmware, but only in their BIOS interfaces. It works exactly as you'd expect on most of my machines but I have two that seem to receive way too many keypresses in the BIOS whenever I touch a key. I've tested it with Macs, PCs from various manufacturers, the Xbox 360, and the PS3, and it works on all of them that I've tried, but you may have a system that doesn't like it.
If you have a system that my board doesn't work properly with, I'll give you a full refund.I'm also looking into adding the ability to reflash the firmware over USB; this way, if it doesn't work right in your BIOS, but I figure out how to fix it, you can download the new firmware and flash it to the keyboard from your machine without even having to open up the keyboard. The USB-reflashable boards probably won't be ready for a few months - I haven't gotten one working yet.