Red Carpet Enterprise has been really well received since one guy can install it in about an hour, and it makes it trivial to deal with software management issues like deploying updates and creating standard package sets for your various machines.
Nat FriedmanOS X is sweet: it's simple and intuitive, and I think GNOME shares a lot of values with it.
Nat FriedmanAs Mono matures, people will begin to use it to write desktop components that take advantage of all the hard work thats gone into some of the meatier GNOME libraries, as well as the nifty language features of C#.
Nat Friedman