Great to hear others think versioning is important too! Then is the question of how to implement it so you can actually find and maintain the different versions spread around your drives. Since PM has the best user interface I have ever seen, and I am not talking GUI here but ability to know what users want to do and when, and cut out the crap (and I have worked with software, and have seen A LOT - actually, if I were a manager at Microsoft I would buy out the people working on PM and put them in charge of Windows, then Apple could get some competition....lets hope this never happens!!!!) - anyway, so I think we could see some fantastic implementation of it!
I would have a look at ID-Imager, that versioning is close to what is needed (but the user interface really sucks, and it super-buggy, but I still use it...;-)
The innovation bit would be to be able to search 300.000 images on all drives, find version candidates and present a suggestion list to the user at the end of the process in a smart way, and, the ability to save the search result somehow, as going through that list of suggested versions could take days and has to be done manually, and the computer could also o crash sometime during the process too, since it so massive amount of data and drives we are talking about.
Perhaps a user settable mix of image name part (*number*) OR/AND capture time (*exact same second*) OR/AND image looks (*thumbs match >90%*)
Talking about crashing.....ID Imager tend to crash on very large imports of the type you do when catalogouing the first time, I can understand that it happens, and that PM will most probably be less buggy, but there should be some kind of auto-resume thing kicking in if it should ever happen, since typically you would have to leave the computer unattended for days to do a really big first scan....only to come back and find out that it stopped after 5 hours, and you dont know what file caused it, so you have to guess and restart the scan.....then you need anger management...;-) Again I am not sure this will be needed for PM, but perhaps worth considering, since a smooth first scan of all images is absolutely vital to gain new users.
Also the ability to cope with changes to drives outside the database, new jobs have to be scanned, and old jobs have moved etc etc. Look at Thumbsplus for a nice handling of all this. The databse is kind of integrated into the standard tree view, just indication what is in the catalogue and not. Much nices tham the Lightroom approach with explicit "imports" if you ask me.
/Petter