I also agree on Be. While I used BeOS (even got to play with it on a BeBox) and was impressed by it, NeXT was the better system. Oh my, networking was a mess in BeOS, and I'm not sure they would have ever gotten full multi-user support.
As a youngster, I pined for NeXT after playing with one at a university lab. I still marvel that we now carry NeXT workstations around I our pockets.
I really wish the Linux / BSD communities had rallied around GNUStep. Would have been nice to see how two implementations coevolved.