I haven't tried Unity yet as I couldn't get it to boot a couple of months ago, but my experience on a buddie's Mac when I was helping out on something real quick was with with lots of windows open, spread across multiple monitors. Now I have to move my mouse across two monitors to get to the app menu? Are you kidding me? Not very intuitive, and very user unfriendly. The Mac UI needs some modernisation to be sure, and dropping global menus should be the first thing done to get it into the 2000's... I don't see why Unity would pick up such a backwards "FF" (Fossilized Feature).
I don't have those problems on KDE which is much friendlier/easier to use on the desktop with 2 1900x1200 monitors, and then when on my Netbook, it uses global menus where it makes sense, and makes the UI easier to use, not harder. Everything has been quite intuitive with Kubuntu in both desktop and netbook mode. Crap on KDE just works the way I expect it to or better these days, which is saying a lot considering the disaster that was 4.0. 10.10's Unity hasn't impressed me on the netbook as much as KDE did. I'm increasingly satisfied with each new release of KDE on normal desktop machines with 4GB ram and decent graphics, so I'll probably stay with it for a while.