1. The menu bar at the top of the screen, which.. I mean, I get why it's there. I get why it's one of the primary reasons that point-to-focus isn't a totally reasonable option to offer. But on a big screen, it's a looooong way to go with the mouse. On NEXTSTEP you had the menu that could be moved around the screen or called up with the right mouse button. I miss this, even though I understand why it was not carried forward for OS X. Context menus are more valuable overall I think, though it would be nice to have SOME kind of solution for having to mouse all the way to the top of the screen every time you want to use a menu.
I run two large monitors on my Mac and I've never had a problem with the menu bar. The way mouse acceleration works on the Mac has always been well-suited to getting from anywhere on the screen up to the menu bar with a single flick of the mouse, at least by my experience. That being said, there were some third-party extensions for the classic Mac OS that duplicated the menu bar as a contextual menu, similar to NeXT. I'd definitely enjoy having that available in OS X.
2. The lack of a "shelf" on finder windows. On the NEXTSTEP file browser you pretty much had to use the shelf to do any kind of file management. It was a big shock for me at first, since I was coming from OS/2 where you could just pick stuff up from wherever and move it around. But I quickly got over it. The NeXT file browser was effective and (more importantly) consistent, so after a couple of days I found the Browser vastly more efficient than WPS or the Windows File Manager for managing files. OS X Finder is a lot more flexible in how you interact with it so the _necessity_ of having a shelf isn't there, but it would still be handy to have it there to use.
I don't like the model of doing file management across directories within a single window to begin with, but for that model, I agree that a shelf is better. The Windows, and now OS X, equivalent to this is Copy/Paste, but the concept of a shelf is more appropriate... just stop and think for a minute about the idea of "pasting a file." Cut/Copy/Paste were never intended to have anything to do with file management.
3. Left function keys, a la Sun OpenWindows. I found having L-keys for things like Open, Front, Props, Cut, Copy, Paste, and others, to be _extremely_ useful. Command Z/X/C/V is close enough for undo, cut, copy, and paste (and Windows is horrible in this regard). I would love to have Open and Front keys, though arguably this is more helpful with point-to-focus than with click-to-focus. I also get why there aren't these keys; it gives the "oh, proprietary" people one more thing to moan about. Props doesn't exactly relate to the OS X interface but some equivalent there could be good. The eject key is a nice addition, volume and brightness I don't use much myself except on the laptop, but I think are reasonble. The PC folks offering "Media" and "Internet" keys... not so much.
Good idea, but obviously not going to happen due to Apple's current obsession with making the smallest possible keyboards. I hate those keyboards.
4. Arrange In Front. On NEXTSTEP one of the standard UI calls brought all windows for the current app to the foreground, and arranged them in a cascade. Once I figured out what situations this was useful in, it was revelatory. I miss it dearly in OS X and it wouldn't be a big deal to add, really. The complication here is toolbox type windows, which were typically not affected but possibly required the developer to do something to explicitly exempt them. I didn't get far in developing for NEXTSTEP so I can't comment on that one.
I've never been a fan of auto-arranging windows and don't think it really fits within the Mac interface, but it's interesting that NeXT did that. Of course, bringing all the windows of a given application to the front (without changing their arrangement) is a long-standing Mac behavior.
1. Hide All. Hide Others is an interesting twist I haven't explored much to figure out its actual value.
Hide Others was very useful to me on smaller screens in the past, but I haven't used it intentionally in a long time. I'm glad it's still there, though. As for "Hide All," that's basically what the Exposé "Show Desktop" feature accomplishes, with the ability to easily restore everything that was hidden (one reason I stopped using "Hide Others" much was that you had to manually bring everything back).
2. Services (once they were put back in 10.3 (10.2?), though in 10.6 now they are somehow less helpful to work with possibly as a result of trying to be more clever)
Services have been in every release of OS X (including the beta), it's just that most users and developers are unaware of them or ignore them.