I know a certain influential blogger has gushed over the U1/U2 dial on the D7000, now replicated on D600. As a D7K owner, I'd like to put a counter-point out there, and maybe collect some opinions from other Nikonians who have found move love for this feature than me.
I find U1/U2 unintuitive and not nearly as useful for me as the (also, I admit, unintuitive but in the end more useful) custom settings/shooting bank selection from the Dx & Dxxx cameras.
Let me walk through how I work, so others can see why I don't like U1/U2.
My typical shooting is either Lanscapes or Birds in Flight. I also like to have a "green" mode for shapshooting which is basically my Landscape mode at f/8 + auto ISO and without any mirror delays.
You'd think I'd set up U1 for landscapes and U2 for birds.
Problem is, my landscape shooting is about 60% aperture priority and 40% manual exposure. Because exposure mode is on the same dial as U1/U2, I can't work within a user bank and modify my exposure mode.
So, I think maybe PASM is my landscape mode, U1 is for the birds and U2 is "green" mode.
Aha. Shooting birds I'm probably 80% manual exposure and 20% shutter priority + auto-ISO. So I can't use U1/U2 for that either.
In the end, I pretty much work on PASM and have to work through all settings when I change what I'm shooting, i.e. it's like the camera doesn't have user banks at all. I do use U1 for my most common landscape setting and U2 for my most common bird setting, so I can quickly jump to them in a pinch, but the user banks don't help me switch my camera between my shooting modes at all.
Ultimately, there's some issues with the pro-body custom setting/shooting bank. Switching them is buried in the menus and I still haven't figured out why they are not tied together. But, here I utilize the favorites menu and access to them is reasonable. The key is, because these are not in any way tied to exposure mode, I can freely work whatever exposure mode I need within my custom settings. Because of this, I find this way much more useful.