1) My uploads have always been approved in less than an hour, including updates to existing UI pieces. Your mileage varies, apparently.
2) I am not an admin/moderator but I think the idea is that the ui will be tested before approval, so this could take some time.
3) Updating a UI is essentially uploading a new file, so it has to go through the same process. Anything could have changed in the UI.
4) I don't think anything ever qualifies as critical for the UI. If there's a problem just delete the file and the default will be used.
5) I could envision a system whereby a certain author is given 'trusted' status so his uploads are automatically approved, but personally I would opt out even if given such status because I know I make a lot of goof ups and appreciate it getting checked. (implementation would probably be more trouble than its worth though).
6) You get what you pay for.
7) Pay for some patience
