1. Workplace layouts are crisper and less liable to move about than in CS4, selecting a preset or custom made workspace layout switches the workspace instantly – unlike CS4 that took ages.
2. Working in CS5 is definitely snappier than in CS4 on the same setup, things seem a little more solid. Having said that there are a few none critical bugs to do with selecting images to copy then paste over other images, sometimes when this is attempted it doesn’t work (or pastes another image from earlier working and not the last one selected and copied). This is the kind of bugette that is removed by a 0.1 release within a few months.
3. CS5 now supports the IPTC extension standard which are extra metadata fields for things like model/property releases. Not too sure if Getty or anyone else support metadata in these new fields yet but I would imagine they could in the future (and simplify their upload process which is very tedious).
You can read more about the metadata extensions here:
http://iptc.cms.apa.at/cms/site/index.html?channel=CH0099
Stephen