Hi Matt,
Great to hear you're appreciating Yummy FTP

I also love to get suggestions, so thank you!
1. Do you mean from the Back/Forward buttons? If so, it's just the way it is implemented in Yummy FTP at the moment. I have an existing 'to do' on my list to make column view behave more like the Finder in some respects, this included.
2. If you mean by holding the Alt key down so that you get the + cursor, then yes I agree that it would make sense to add that. Someone else asked for this recently, so that's two votes for it already.
3. FXP (File eXchange Protocol) to do true server to server is planned for the future, but it gets pretty messy when dealing with complete directory structures, which is the main reason it's not been implemented yet. As an interim solution I might be able to add FXP for single file transfers, though - it would certainly help with those huge files

4. Tabs are planned for the future, too
-Jason