Portable means portable, it's a somewhat standard concept. It is genuinely a showstopper for me as i'm often jumping from computer to computer with my programming projects on a usbkey. I was thinking it might replace pen and paper which suffers no such issue.
For the sake of having a simple parameter setting in the application to replace appdata it is likely it's driving a few away who might otherwise contribute. Say by adding parts like the attinyx4 series.
I hope this is taken as constructive feedback.