It took me maybe 4 hours not rushing to install. Paid $68 bucks.

It mostly eliminates that shuddering you get when engaging 1st and reverse. Real improvement.

I really didn't notice a spectacular improvement in throttle response or the overall tightness of the car, but it definately did improve the feel of the drivetrain. (I did my grounds at the same time, and I was more impressed with the improvement they made.)
I really noticed the brace when I was driving around a parking lot in 1st & 2nd. Tighter and more direct. My cold exhaust no longer rattles either.

So if your engine shakes alot in its mounts, this $68 mod is an essential. 2 thumbs up!

 

Or just switch to convertible or Mazdaspeed engine mounts.