I personally love TNA, but then I like classic pins a lot. I think that most of the old Stern games are super fun, Seawitch, Stars, Meteor, Cheetah, Star Gazer. Awesome, awesome, awesome. TNA has the same feeling. Ripping the spinners in TNA is just like playing those games, with added modern touches.
The music of TNA, the speed, the ball save timer, the unique layout compared to most games today. It's a blast. Yeah, the art is meh. In my house we consider a C to be below average, so I'd give the TNA art a B to B- maybe? The game definitely very linear, but I don't mind that playing it on location. Were I to own one, it might get old if it wasn't part of a reasonably large collection though.
I'm always amazed by how many TNAs are on location. They've "only" built a couple hundred of them and they seem to be on location EVERYWHERE. I've seen it at Sunshine, Eight on the Break, The Pinball Gallery and Rock Fantasy. That's a testament to how much people like it.
I keep toying with the idea of getting one. I think that I'd love having one for myself, but I know that my kids and wife would like a licensed theme better. Plus, they're tough to come by. I'd rather go with a newer Stern Pro in the high $4s than $6 - $7 for a TNA. Some guy in my area bought a HUO TNA with a butter cab for $7G, put it on location and is now trying to sell it for $10G! Ten thousand bucks for a routed TNA, no thank you.