[I was going to send this to sbcl-devel, but I've already pestered the folks on the list with a couple trivial matters this week and I'm sure the folks have better things to do than listen to me whine about perceived (by me) weaknesses in SBCL without a patch to address them. So, here goes...]
I'm sure there are more pressing matters in getting SBCL to 0.9, 1.0 and beyond, but I'd like to suggest that the SBCLHOME/INSTALLROOT thing is too fragile and should be fixed. To require that INSTALLROOT be set at build and install and runtime seems overkill. I would prefer to see SBCLHOME/INSTALLROOT be set at build and install time, leaving an sbcl executable that doesn't require the setting of SBCLHOME. I think this will help make SBCL useable for new users. I understand that 1) this is a relatively trivial bug, 2) there is a number of simple (including some currently documented) workarounds and, 3) there are more important things to work on, but, nevertheless, I think it would make life easier for folks who are new to either Lisp or SBCL.