The general configuration of the A100 is standard and is easy to use if you have any experience with operating an organ. If you don't have any experience, it is easy to follow and you should be able to figure it out pretty quickly. The presets make it easy to choose between a bunch of different organ sounds, but the draw bars and vibrato effects also come in handy to create your own sounds and especially if you don't have a Leslie cabinet to use this with. I don't have a manual for the Hammond A100 organ, but it is pretty easy to use and figure out that I never need one.
The Hammond A100 is great for all types of music, but I have used it mostly in rock and pop. While it doesn't have the same quality as a Hammond B3 or C3, it sounds good and is a good substitute for these organs if you can't spend thousands of dollars on these top end organs, like most of us. The feel of the A100 is smooth and is definitely has an acceptable expressiveness to it. While I always try to use a B3 when recording, if that isn't possible the A100 works great.
I've been using the Hammond A100 for a few years here and there for studio use and it has always produced good results for me. It is easy to use and has a great sound to it. As I stated before, this won't compare to a B3, but is an acceptable substitute especially considering the price difference. The A100 is a great choice for the player who wants a real organ at a reasonable price.