I agree with bose-x. GA needs to be dragged (kicking and screaming as necessary) into the 20th century. It's the 21st now but let's keep the objective managable...
"All of which would require the pilot to look in even more...."
Beagle, I am sorry but I really disagree. There is no need to look down because the system gives you an audio warning. I have a cockpit full of gear so I know. Cockpit automation allows much more head-up. An autopilot tracking the GPS is the dogs bo*****k and the head-up time is at least 99%. I am not under any illusion of spotting traffic (for reasons I've stated here plenty of times) but the view is usually nice to have
Unless, of course, the pilot doesn't know how to use the gear and is fiddling with his knob(s) en route. But that's a whole different issue; it IS possible to buy a plane with all the kit without having training on it (wrong IMV). Most PPL instructors haven't got a clue when it comes to avionics (vast majority of PPL instructors can't even load a route into a GNS430) so it's no suprise they are scared of it. Those instructors that do understand it are, IME invariably, very keen on a pilot knowing it and using it. Cockpit automation -> low pilot workload -> greater safety. The airlines learnt this decades ago, but GA lives on in its 1920s "Humphrey Bogart romantic era of aviation" time warp.
Also the terminology is being used loosely, including my myself. TCAS is the wrong name; there is no need for an advisory action or for automatic resolution (which would imply an engaged autopilot with auto throttle etc etc). The TCAS climb rates are a redherring; a jet flying at 250kTAS will be doing +3000fpm even on a small gradient. One just needs info on traffic that's relevant (according to its extrapolated trajectory).
Radar cover isn't a solution either. Most traffic reported by RIS cannot be seen, no matter how hard you look. So, OCAS, this doesn't really work either unless one takes action early on, but few units will give you an RAS (especially when needed) due to the very generous separation rules required being quite impossible to achieve under conditions of any traffic density, and when you do get an RAS they make you fly anything up to double the distance, with 90 degree left/right etc. I never ask for RAS for that reason; an informal "20 L/R" vector from a radar unit is much better.