Err, yeah, except the advantages of IPS far outweigh those of a high-end TN panel.
TN advantages: somewhat smoother (if you can notice it) gameplay.
IPS advantages: better color reproduction, better viewing angles, and higher contrast ratio.
While it is true IPS generally (not always) offers those advantages, it's entirely subjective to say those advantages outweigh the smoother/clearer motion on TN. For some, the most important aspect of a monitor is how well it handles motion blur and ghosting (clarity and smoothness of motion). For some, it's picture accuracy. Some, like me, are somewhere in the middle (or, rather, want both). To say one aspect is more important than the other comes down entirely to one's needs, tastes, and tolerances.
Have you seen a good TN monitor with 2D LightBoost at 120FPS? The additional motion clarity was a more striking improvement to me than moving from a basic TN display to a nice IPS display. However, I'm also sensitive to any sort of stuttering or low framerate and play games on my computer more than anything, so I was more easily able to appreciate the difference. I know some people who can't tell the difference between 60Hz and 120Hz or with/without 2D LightBoost, so a person like that would see little benefit in TN over IPS. There are also plenty of people that would be unable to tell a difference between a good TN panel and a good IPS panel but might be able to appreciate smoother and clearer motion.
For me, the sweet spot is my 1440p IPS overclocked at 120Hz (I can never, ever go back to 60Hz regularly...even 96Hz starts to strain my eyes now). It has more motion blur and ghosting than a really "fast" TN at 120Hz, but it's negligible in nearly all situations (IPS looks like a smear fest compared to a monitor with 2D LightBoost enabled).
Many of you are over-simplifying the issue to prove your points. It's not a black-and-white scenario.
To the OP, if you are most interested in 120Hz and don't need perfect picture quality and accuracy, I would recommend getting a 120Hz monitor with the best image quality you can (assuming it's in your budget). As a gamer, 120Hz is more important and more beneficial to me than better picture quality, because it's not like decent TN displays really look that bad (unless you are constantly looking at your monitor from an angle like a weirdo). The only compromise I've found are the Korean 27" IPS displays that SOMETIMES overclock to 96-120Hz. I'd give up my IPS in a heartbeat if I couldn't do 120Hz on it...I just can't go back to 60Hz.