The make up of the Standard Audio Level-Or is generally pretty simple to follow. It's got the configuration of a limiter rather than that of an overdrive, with parameters for input and output levels and switches for mode (between level and crunch) and for choosing between a fast or slow release. I haven't seen a manual for the Level-Or and I don't believe that one is necessary anyway.
It's possible to get some really interesting tones with the Standard Audio Level-Or. While many compressors and limiters out there will give you some drive if you crank them, most aren't designed for this use so there is generally only so far you can go with it. But with the Level-Or you can take this sort of compressed overdrive to a whole new level. The level and crunch modes are pretty different, where the level mode is more of a straight up heavy sounding limiter and the crunch has straight up overdrive/distortion. Between the two modes and the other parameters you can get a variety of different types of tones, all of which are realistic and full sounding.
I don't have a bad thing to say about the Standard Audio Level-Or. It does exactly as advertised and actually exceeded my expectations. While perhaps not a necessary piece of gear for 500 series rack owners, it's definitely a nice luxury item to have for those who are looking for something like this. If you find yourself trying to get some overdrive for your compressor/limiters, just get the Level-Or and do it with ease and flexibility!