I am a fan of Nautel but have a client with several Flexivas that he absolutely loves. I mostly do AM work for him so haven't had occasion to even see them.
I must say that I have had much more infant mortality problems with Harris/Gates & BE over the years than I have had with Nautel. Others report quite the opposite but that is my experience. I am really more concerned with the financial stability of BE and GatesAir than the quality of the equipment although I have not had very good experience with BE's modern FM offerings.