The pads for the small-signal transistors are just too bloody close together!
It takes a super-steady hand, fine solder, and a lot of skill to install them without bridging the solder pads; it takes even more skill to un-bridge them without causing some traces to lift off the board. I'd suggest that the pads be laid out in a traditional "diamond" (triangular) arrangement in V3.1 boards, if possible. That would make it easier for both new and aging veteran kitbuilders to assemble.