I'm wondering what open mappings are actually good for (except for inverse becomes continuous)???
My irritation came since, people stress that an open mapping not necessarily preserves closed sets (well, sure, I mean closed maps are some totally different subject since they don't describe neigbborhoods).
I cannot imagine any other purpose despite quotient maps or homeomorphisms but thats again about some continuity issues; maybe you know some problem where this becomes really important...