I once had a back and forth with a LR developer where I asked why LR would not import/recognize Adobe's own PSB large file format and was basically told it was impossible (for reasons that seemed totally made up at the time). I wasn't even asking for the ability to edit these files, just the ability to display them in LR. Turns out those reasons were made up. It is so easy to hit that 4GB file limit when blending exposures, merging photos, panos, focus stacking, multiple smart objects, etc. Well, the latest version finally supports it's own PSB file format. About time!
If you were previously doing a work around to edit PSB files in PS, I've found that after upgrading LR your PSB files do not automagically appear. You have to to go your root folder in the "Folders" pane in LR and right click on the top most/root folder and then select "Synchronize Folder...". This will only work if you had saved your PSB files somewhere within the file structure of your existing catalog. In other words, if your LR library resides on, for example, drive "G", those PSB files must also me somewhere on drive "G" for them to be picked up and imported using the synchronize function.
