Hasu,
I must thank you for your work on this converter code. I've tried a couple ps2->usb converters for my trusty old Dell AT101W, but with limited success, often they would not always register Shift properly, or would just have terrible rollover effects (keys repeating, missing, etc). I've only been using your code + teensy 2.0 for a few hours, but it's already worlds better!
I am still having one strange issue, and I am not sure what the cause might be, but some of the punctuation chars (? and ; keys) work, but have a large delay in triggering. Seriously delay, easily 100+ms delay from when I press, to when it actually inputs. Yet the other keys, all around them, are 100% fine. Obviously this doesn't happen on another machine that has a direct ps2 port still.
Any thoughts on what that could be? Is there any diagnostic information I could provide you? In my build options I have extended keys + mouse keys disabled, NKRO enabled.
Thanks again for a great tutorial and code!