Quoted from HoakyPoaky:

TNA has more going for it than just destroying reactors & rinse/repeat. While the gameplay is straight forward, it is really difficult to master. I love that type of gameplay. Bowen makes EVERYTHING look easy, so judging TNA based on watching him is completely misguided. Most people on average are lucky to destroy 3 in a single game.
The challenge lies not only in destroying reactors, but in maximizing the reactor bonus first, then destroying the reactor during multiball for the 3x multiplier. Scoring huge points where the fun lies (for me at least) & proves a long term challenge at home. If your only goal is just to see how many reactors you can destroy, you are missing a whole other level of strategy on TNA. And the difficulty of making those shots increases as the game progresses (alternating orbits, restarting multiballs, etc). Oh did I mention scoring super jackpots at the scoop during multiball? Yeah good luck scoring those on a regular basis.
What looks like a simple game to some is actually layered with scoring depth. Plus there's the insane lightshow, the music & sounds, the classic 80's Bally design, co-op gameplay, the ass-kicking nature of the gameplay that forces you to play better, and on & on. It's a long term keeper for me. Different strokes for different folks tho.
I only played IMDN once, and thought the ball times were long, the shots were easy to make, it had great scoring rules, and it's pretty sweet too. Just depends what you're looking for. You want a modern classic or an 80's classic?