This easy drop-in replacement idler eliminated the noise and vibration I had with my old stock idler. The thrumming vibration of the old idler was particularly annoying. Granted, an expensive new idler isn't everyone's cup of tea, but I like well-designed and well-built products, and I'm happy with the T-Cycle idler. On top of that, the company is a pleasure to deal with.
Fit and looks good.
I don't have the instruments to measure the power loss due to friction between the crank and the cassette, but I do have ears. I can tell you that this idler makes my bike almost silent when I'm pedaling. I didn't notice the sound the stock idler made until it was gone, having upgraded to this one.