Using the Tech 21 XXL Original isn't very difficult as it's got some pretty basic parameters to work with. The three basic ones that you see on pretty much all distortion and overdrive pedals are it's parameters for level, tone, and drive. However, it also has a knob for warp, which is a unique parameter to this pedal and essentially seems to work as a resonance filter. A manual shouldn't be necessary here.
The sound quality of the Tech 21 XXL Original is outstanding all the way around. There is a reason that these pedals are quite popular and it's mostly because of the great sound it's got. It's a really thick and meaty sort of distortion, and it's definitley more of a traditional distortion than overdrive or fuzz. The warp parameter opens up a new palette of sounds, as this isn't a typical parameter and it allows for some really cool potential manipulation to your sound.
The Tech 21 XXL Original is definitley a pedal you should consider if you're looking for a distortion pedal for your guitar or otherwise. While it wouldn't necessarily be my first all around choice, it's still a very good one and is a pedal absolutely worth exploring. The price is pretty reasonable for a pedal of this type, but this isn't going to be the best bang for your buck out there. This pedal is definitely the real deal, it's just a matter of what color you'll prefer...