Just wondering if anyone installed one of these. If so, how easy was it to install and how's the quality?

 

I haven't installed it in an S2000 or any Honda/Acura for that matter, but I have installed it in an Explorer, a Grand Cherokee, and a few other vehicles.

Install isn't difficult, but it works mediocre at best. As you probably know, the Neochanger connects directly to a factory head unit and is controlled by the factory head unit. With every unit I've installed, the response to the controls are very slow and do not work at times. Not worth the money in my opinion.