A lot, I think. PA-RISC had a lot going for it, high performance, solid ISA, even some low-end consumer grade parts (not to the same degree as PowerPC but certainly more so than, say, SPARC). It could have gone much farther than it did.

Not that HP was the only one to lose their minds over Itanic (SGI in particular), but I thought they were the ones who walked away from the most.