Update by Tim Suddard to the
Unless they revise the lower ratios, the only thing you might get with that swap is an OD ratio above the 1.0 4th gear. Very nice mod if you find highway travel gets bit tiresome with the stock 1.0 ratio and whatever diff is in the car, but not much benefit if you are never topping out 4th or at least running at a speed (likely illegal) that results in an unpleasant noise level.
If one is after performance rather than comfortable cruising, they are well worthwhile - it means that you can drop the diff ratio for better acceleration while retaining top speed capability of the original stock diff. I ran a close ratio set of gears plus and overdrive in my MG race car that allowed me to go from a 4.3 to a 4.55 which resulted in significantly better acceleration plus the same top end. I also enjoy the 6 speed box in my Z4M - gives you a very close ratio set for the first 5 gears (5th is 1.00) plus a nice long cruising overdrive 6th speed.
