I played Tron quite a bit back in the early 80's when it first came out.. hell, my local arcade even had organized competitions with the Tron machines! To me, it's all about the nostalgia and when I fire my machine up, the sounds/music trigger my younger years, and that's the reason I have my machine.
I really don't think the gameplay is any better/worse than any other machine of the era either.. sure it's a tough game to play, and if you are impatient/don't care to take the time to defeat or master it (like a lot of people did in the 80's), I can see why you would be quickly turned off.. but then again, to me, that applies to any game of the 80's.
I also have a DOT and consider that a better game also.. but Tron fits in for both cabinet looks and gameplay for me...
If you didn't play the game in the 80's and get hooked, I could see why it doesn't jive now.. doesn't make it a turd by any means...