Hi,
I've been using PM and PM+ as well for different purposes:
PM on my daily work with local files
PM+ on my photo archive
Back in the old days when i used ACDSee, there was a neat feature that i'm really missing from PM (i can find it in PM+ tho).
There are situations, when in browse through folders and collecting files based on specific criteria by looking at them (so aestethics criteria and not technical filtering/search). Back in the old days there was a feature called Image Basket in ACDSee and with a handy keyboard shortcut that was basically a default built in collection (in PM+ terms). When i added files (or at least shortcuts to the files) to this to this bin, it was easily done with the keyboard shortcut while i was changing folders, opening and closing "contact sheets". Adding a file to the basket doesen't need to write anything to the files themselves (like tagging) or it doesen't need to be a database. In technical terms it's just a simple list of files (shortcuts to files) that i can add and remove images to/from multiple sources/folders.
After i collected the images into this collection/basket, i usually export/copy them to another working folder and i usually clear the content of the basket, so the collection doesen't need to be permanent. It's a virtual list with references to files, not an actual file storage location.
I don't need the complete fully customizeable implementation of collections that is available in PM+. All i need is one simple temporary list/basket of files where i can put shortcuts to those files and i can collect/export those collected files for further use.
Nowdays if i want to do the same/similar functionality, i need to combine different folder's contents into one contact sheet first. And use tagging, that modifies the file (if i'm correct). I don't want any permanent modification to the selected file, i just want it to be added to my list. Keeping that list visible and intact (maybe as a window pane), while freely wandering and roaming between folders and contact sheets.
I hope it makes sense and others might find this feature useful and i hope it's not something that's already available in PM.