I'm not the biggest fan of Boss pedals, but I do have a couple of favourites, and the CH-1 Chorus is definitely one of them.
CH-1 is a very smooth and clean sounding chorus effect, that compliments any clean guitar signal beautifully (always works great on overdrive). It works great in mono, but also has a stereo output - stereo chorus is always cool!
The features and controls are fairly standard for a chorus pedal - depth and rate control the sound and speed of the chorus whilst E.level is an effects level, acting as a wet / dry mix. The CH-1 also includes an additional function in an EQ knob, which can give give a really strong, bright and shimmery chorus sound, whilst boosting the depth at the same time can create a sound verging on the edge of vibrato!
The CH-1 is an excellent chorus pedal, offering a flexible modulation which is easy to use. There are many chorus pedals on the market, many with more features, but the CH-1 sounds great and can hold it's own amongst it's competition.