Just posted a long reply on greasemonkey's thread about the IRP shifter. I'll paste it here, but this thing is pretty awesome.
Omgpham video was definitely informative, he no doubt has quality taste.
I got it overnighted by Burstcraft on Thursday and threw it in for day at the FIRM the following day. Install is pretty simple with a couple annoying bits like the center bolt.

The other videos you can find online pretty accurately give you an idea of just how engaging and short the throws AND the side to side gate action is. There's also a set of screws that you can adjust to get ride of any size to side play which is pretty trick too.

Never felt anything like it, including the couple MR shifter I've grief in others cars. If it was in a straight up race car, you'd think, "yeah that makes sense."
Side note, it's aluminum, much lighter than it looks or I anticipated.
I essentially bedded in some brake pads and used the shifter for a good 10 minutes on the street and that was all I got because I chose to trailer the car to the track. But during that time, it was a really short learning curve and wasn't worried I'd have an issue at the track. Gears go in very naturally and probably cut my shift time in half. (Disclaimer, Miata shifter is already great, well except the 6 speed.)
Over 4 sessions, I never missed a shift, except once I went to 5th instead of 3rd, chalk it up to gates being really close.
Negatives.
It got warm on track, street I doubt it.
It's relays more NVH and noise at my very upper rpm and allows whatever noise your engine and drivetrain currently makes into the cabin.
The rubber gasket shift boot is thin and not said quite right so there's basically open air to the tranny tunnel.

I think the last 2 can be remedied by some foam, sound deadening material and carpet.

Here's a video of it in action.
https://youtu.be/aI0BU_7VO1A