dartagnan, reading the mostly entertaining answers, I come back to your original questions:
nowbody knows airbus' system
On modern aircraft you have a slightly different approach compared to more "mechanical" aircraft: You don't know everything anymore. Hardware is possible to know, but with the arrival of software, it is impossible to know every line of programming code and what it is doing at which position. This is no difference to other modern aircraft, like a Saab 2000 or other FBW aircraft. That's also the reason why AI hands you out a rather basic FCOM.
switch off computer if everything goes wrong
This is basically a good way. Remember Airbus golden rule: If it doesn't fly it the way you want, switch off the autopilot. That's no difference to any other aircraft with an autopilot.
If you are coming from a previous aircraft without auto thrust/trottle, you might be astonished by the complexity. An Airbus has basically the same autotrust functions as any other aircraft of its class.
lot of different systems/abbreviations
This is also true but mostly standard nowadays. Even a F100 has FADECs. There might be a few more systems on an Airbus but I'm sure that Americans like Boeing knows much more abbreviations.
flying compared to conventional stick
its just a matter of training. If you are unsure, install yourself a MS flight sim (now version X avail!) and do some training. On the real aircraft you will be astouned how precise it is (a characteristic of most French planes), and after a few 100 or 1000 hrs of flying (hopefully a few of them flown by hand) you will realize that this aircraft flys nearly like a "normal" plane: you have balloonig effect with flaps setting, you feel small wind changes during landing, you feel a gust and make a small correction, you flare and feel the wheel touching softly the ground and grease it on the concrete.
All of this you will only experience if you still try to fly it like an aviatior. One problem is that Airbus doesn't encourage you to fly it like a normal airplane, even some airlines don't (no visual, no manual flying). People become slaves of the system or like robots. I see that sometimes when people flare the 320 always exactly at 20 feet, when the system calls "retard".
Enjoy it!
Dani