The Empirical Labs Derresser is a high quality outboard de-esser that I believe will fit into any lunchbox style casing and therefore isn't rack mountable. I'm not too sure about the connections as the one that I have used was pre racked already in a studio.
The make up of the Empirical Labs Derresser isn't too hard to follow as everything is pretty straight forward. You've got parameters for threshold and frequency as well as buttons for high pass/low pass filter, high filter limiter, and bypass. Even if you don't have much experience with dessers, as long as you understand the basic concept for this unique dynamic processor, I don't think you'll have any trouble figuring it out. I haven't seen the manual, so I can't say how well put together it is, but it is easy enough to use that I don't think one is necessary.
The sound quality of the Empirical Labs Derresser is top notch. This is definitely one of the best sounding dessers that I have used, although I haven't used all that many different outboard dessers. I have only used this for vocals as that is what a desser is generally used for, but I guess that if you wanted to get less sizzle on another instrument, this would work fine. This is also a pretty versatile desser compared to the other ones that I have used, making it great for pretty much anybody's voice...
I first used the Empirical Labs Derresser about a year ago and since haven't had the chance to use it since I don't own one myself. Hopefully I can get back to the studio that I used this at soon as this is a great tool to have around. It ranks up there as the best outboard desser that I have used and is probably just as good as you are going to find one. It is easy to use while maintaining a great deal of versatility in addition to its top notch tone quality. If you are looking for a great sounding desser, the Empirical Labs Derresser is a great place to start.