[throwaway91111]

I don't think this is correct. There's a constant 1G force; you can adjust for the difference necessary in angular momentum as you turn. Sure you won't be perfectly level in the same way have a constant rotational velocity would be but it's still a barrel roll.

Of course, it would point in a different direction, but the magnitude would be 1G.

Hell, i think you could easily develop an intuition for it.

[falcolas]

The 1G is from the frame of reference of the passenger. Gravity's effects are essentially nil for the passengers (and the aircraft itself), since everything in the aircraft is accelerating in the same way at the same time. You only really feel the force of the lift generated by the wings.