anyone using the same setup or a similiar one? what kind of differences did you notice?
Yes, it's part of my dual sprocket setup. See the pinned thread in Performance and Customization. I added the 55 because I live at 6,000 and ride to 10,000, and sometimes even 13,500 on a trip to Colorado, for instance. The TW doesn't have much oomph at that altitude and needs all the help it can get, besides re-jetting. You will need a 124 link chain.
I really like it for rough, steep terrain, it makes technical sections much less hairy to be able to go slower without clutching. I can get up to 55 mph on the pavement, but 50 is really a more comfortable top end. Gas mileage goes down to around 55 mpg, but since these types of slow technical rides are not usually over 50 miles long I think it's a good trade-off.