I found that using the Manley Langevin Stereo Variable Mu was generally a pretty easy thing to do. I will assume that those who are using a high end limiter like this one will probably have a bit of experience using other limiters and compressors, so if this is the case, these users should be able to adapt quickly to using the Variable Mu. Each of the two channels has it's own parameters for threshold, output, attack, and recovery (release). There is than a dual input know which controls the input level on both of the channels. In addition, each channel has switches to choose between either a compression or limiter mode, for bypass, and there is also a single switch to choose either a linked or separate connection between the two channels. I haven't seen the manual, but I think the Variable Mu is easy enough to use where you don't need one.
The Manley Langevin Stereo Variable Mu is capable of being used in all sorts of situations and scenarios. While it is first a limiter and then a compressor on paper, I would say that it has equal capabilities to do both sort of dynamic processing. The sound in general has a very good balance of clarity, sharpness, and girth. I love the way that it sounds on vocals, which is really the only application that I've gotten to use the Variable Mu for thus far. Judging by the way it sounds on vocals alone though (and I've used it on a few different voices), I would say that this can be used for a variety of instrument applications as well. I've yet to have the chance to prove this theory though...
The Manley Langevin Stereo Variable Mu is definitely one of the most popular products that Manley has to offer, which is saying a lot considering their impressive line of high end pro audio gear. I love the gear that Manley Langevin has to offer, although it can be a bit pricey at times, including with the Variable Mu. However, this is absolutely what you need to expect from high quality signal processing like the Variable Mu. If you're a professional studio owner or engineer, the Variable Mu is something you should absolutely check out, but if you're a home studio owner, this is probably a bit out of your price range.