Are there any gotchas/downsides to enabling Advanced Item Location Configuration that I should be aware of?

Maintenance is AWFUL!!!! I try to avoid it at all costs

That's unfortunate to hear. I was hoping that would be an easy way to store the standard on kitted items for reporting. Guess I'm back to looking at a custom record.

It makes the Locations sublist on Item records a separate record type that is joined to the item. So any settings at the location level need to be added/updated per record now. The view is really hard to figure out for most people as you have to switch between different views to see On Hand qty, Available Qty and other location values. It doesn't automatically make inventory-location records when you create new items so its a very manual process to add/update those each time

Yeah that's what I'm doing. I need to roll up kits on a report so we can see the sum of the member item standard cost without having to manually collate this data.