I started using a tray several years ago after developing a tremor. The tremor is gone (beta blocker), but I still use a tray when flying responsive models. When it's a trainer or the like it's not worth the hassle. A tray does have a couple of drawbacks. You can't easily lift up the transmitter to use it for blocking the sun, and you have to move your eyes a lot if you need to look at the transmitter, to find a particular switch, for instance.