It's worth noting that on the D7000 & D600, you can program the AF-L/AE-L button to act as AF-ON. The only reason I can see this causing a problem is if you use AE-L/AF-L in conjunction with AF-ON, because on D7000/D600 you can't have both. While some here do work that way, I've never used the AE-L button so I don't mind losing this feature to gain AF-ON.
I'm a long-time dedicated AF-ON'er and have D7000 configured like this, and peacefully coexisting for nearly two years with my D300s and more recently D800. IMO the lack of AF-ON is completely overblown.