I decided to start painting the Baneblade with the spray gun this evening. I figured it would be a snap, or a total nightmare, so it was my sole project. It went surprisingly well. I read the GW instructions on their website a few days before, so I knew to get two cans of propellant. The instructions that come with the spray gun are incomplete, so I advise watching the video or reading the instructions online.
As discussed online, the propellant gets cold as you use it, with a corresponding drop in pressure. You need to have a second bottle handy while the other one warms up. Sure enough, I was just finishing up the Baneblade when the second bottle began losing pressure. The first coat took about 15 minutes from beginning to end, compared to the 2-3 hours it would have taken with a brush. Clean up was simple with water. I used nearly a whole bottle of paint, so there wasn't much to pour back in the bottle.
Also, one minor issue: Be careful when attempting to mix the paint in the glass bottle. I recommend you stir it rather than shake it, as the bottle is not completely sealed when the cap is screwed on. I ended up getting paint on my shirt.