Yea the TWM STS is a wonderful product. I have one in my '08 I4 5spd and it works great. You will definitely notice a difference and they even included solid shifter bushings with their kit. If you also want to save money you can package the STS with a shift knob and you will have a pretty decent shifter setup. If you have any questions about it let me know.
By "legit", do you mean "is it street legal, and will my car pass inspection?"
If so, then yes. It is about the same length as the shifter in my old Miata.
If you are asking "Is the TWM shifter a quality product?", then my answer again is yes. I purchased the TWM 5-sp shifter with their M1 Abrams shifter knob about 3 years ago and have been happy with it's performance to date. If it has one fault, the metal shift knob gets bone-chilling cold on winter mornings. A pair of leather driving gloves resolves that, though. But that's an [expected] issue with the knob, and not the shifter itself.
Just to reiterate this, it IS street legal. The shifter will NOT do any damage to the transmission. It's a quality product and delivers smooth and short throws. I have it in my 04 GT and my shifts are much more solid. I'm on my way to get an A6 Leopard Engraved knob and cable bushings from them sometime soon. TWM is a great company, and their products have served me well.