This change was made in 5.0.2:
• Collection listing leaves item view selected when changing collections to allow for use of keyboard shortcuts on items.
It's no longer possible to repeatedly use up/down-arrow keys for sidebar collection list navigation, which was convenient for me, because input focus now insists on being on an entry whenever a different collection is selected.
Also, Tab key usage behavior (with/without modifier keys, e.g. Control) can be hard to predict. Sometimes it makes the Title field editable, which I've never liked (in any app) because of increased risk of accidental modifications. Sometimes it moves input focus to the toolbar search field, or into "focus limbo" where further keyboard input seems blocked. For a comparison, (Shift-)Tab works consistently in iTunes.
I might follow up later with suggestions to improve this but just wanted to mention it now.