As you mention, TnT is short for top and tilt. It essentially takes the mechanical screw links the typical tractor comes with and replaces them with a hydraulic cylinder controlled from the driver area via a set of valves commonly called spools. The hydraulicly adjustable top link is extremely effective, more then I even want to start describing. Suffice to say if your dealer calls it a "lazy mans gimmick" he's either an idiot or simply has little or no experience with tractors having TnT. The tilt cylinder(s) allow you to tilt attachments on the 3 pt hitch like box scrapers or blades etc. It can be very useful for cutting a ditch or getting a slope back to level. I have a 3 spool valve. The third is there to allow me to hook in things like the hydraulicly activated rippers on my box scraper or the numerous hydraulics on my Harley rake.
By far though, having a hydraulic top link is one of the most useful devices you can put on a tractor to enhance it's productivity whether your doing earth type work or even mowing especially over banks like you might have if you have a pond or driveway areas where you need to back up to the, to cut. My opinion is that not only is it an extremely valuable addition but it will be money very well spent if you do much of any work with your 3 pt hitch. The factory setup is not cheap. Mine is not factory and still cost me about $1200 for 2 Gannon cylinders, 8 quick disconnects and all the many associated hoses, 3 spool valve, power beyond tap, and supporting bracket for the valve. I like it.... /forums/images/graemlins/wink.gif
Attached is a lousy picture in which you can barely see my TnT spool setup. I had a good picture of it but seem to have misplaced among billions and billions of other bits, bytes and nibbles.