Does anyone know how the bogies are actually held at a specific tilt angle? Gravity seems a little iffy -- I assume the pivot point has to be centered between the axles to distribute weight evenly on the ground, so presumably the bogie's balanced pretty well. It seems like a fairly simple spring could bias it to one stop or the other without too much fuss, though.
The tilt angle must make an aerodynamic difference. Maybe it can be reversed or adjusted during design if there's excessive buffeting (or something like that) with the gear down?
Finally, though I doubt this is a significant design consideration, I'd guess that toes up or down affects wheel spin-up (and perhaps tire wear). The tires that touch down first are under very little load until the other axle touches, so it seems like they'd spin up more slowly.