Dave, the build works pretty bad. Although it even doesn't crash too often (while a lot people say it does), the biggest problem is that it <censored> up the shared memory arena and I can't run programs even after I close FF (sic!), also it doesn't free memory at all -- closing tabs doesn't increase the amount of free memory in the system. Also when I open tabs back again, it eats even more memory, so that's literally a memory-waste-machine.
Strange. I just did a quick test with FF 17.0.5 beta2 (which works well, for me). I don't see low memory usage change, at all, after starting the program. Shared high memory doesn't change, just by opening tabs. It does go down a bit when those tabs are populated. I didn't see the memory returned until I closed FF. There is, of course, some memory that doesn't get returned, but that seems to be normal for most programs.
FWIW, the worst shared memory eater, that I have seen, is CLAMD.EXE, and it gets worse with every database update. I had to quit using that more than a year ago. Since then, I have had no trouble with shared memory.
One thing, that seems to help with shared memory space, is to have the line
dllbasing=off
near the top of your CONFIG.SYS. That allows OS/2 to make better use of shared memory, at the expense of a very slight decline in performance (not noticeable, unless you are still using a 486 SX processor).