IRA has bugs but I've been using it a lot and it does the job. R means "reassembler"
I remember reassembling BattleChess from IRA disassembly and it worked.
It has bugs, but nothing that can't be fixed by post processing. I've already written python scripts to fix some instructions that don't work (BTST #xx,y). I've already written some code to try to recognize text in data. I can dig that up if you're interested.