After putting it together on Saturday, I put my first two batteries through my x450 this morning. I prepared myself by watching Ali Shanmao's heli tutorial vids, quite useful.
At first I tried in the middle of a big field, but there was quite a lot of wind. While it was relatively easy to push the stick towards the wind and compensate, the wind made it quite hard to hover at any fixed altitude. After half a battery I gave up and moved to a more sheltered spot.
The other battery and a half went as planned (for a change, lol). After hovering, I practiced hovering at an angle and then moving slowly from one spot to another and hovering again. Definitely more practice needed, the batteries are charging again as I type.
I haven't even considered trying acrobatic mode, I think that will be like learning a whole new copter again. I practiced a bit with a heli on the simulator, but the real thing seems a lot more touchy than the heli was. I think I'll try some expo, on the throttle at least.