Using the basic features of the Roland AX-1 isn't too difficult, but there are a lot of features that I do not know about since I don't actually own one of these. The typical functions are easily located and after playing it for a bit I felt I had a good grasp for what it is about, but there are definitely a lot of options and features that I have yet to unlock. I haven't seen a manual for the AX-1 so I can't say anything about it, but if you aren't an expert with MIDI controllers and want to take this in depth, then I would recommend trying to get your hands on a manual.
Since the Roland AX-1 doesn't actually have any sound patches of its own, the main thing that I look for in a MIDI controller like this would be its feel and its features, and I would say that the AX-1 excels in both of these categories. It is an easy keyboard to play and has a great action, unlike many of the MIDI keyboards out there that are virtually unplayable. While I've only used this keyboard a handful of times, if I were looking to pick up a MIDI keyboard in this type of form, the AX-1 would be the first place that I would look because of its high quality and reasonable price. While I can't say this is a necessity for any keyboard player out there, there's nothing wrong with a little flare every once in a while...