Here in the states one gets far more courtesy from motorists on a trike than on an upright bent or wedgie. I have to assume that many drivers are simply perplexed by the trike... some thinking that it's some form of wheelchair.
I have dealt with many aggressive and discourteous drivers while on an upright two wheeler, but have actually had to stop and encourage motorists to pass me on the trike.
Yes, they can be more dangerous in certain situations, and require more vigilance from the rider. I had a close call from a vehicle that was "tail-gating" a van, and had no way to see me. He swerved dangerously close to me as they passed, then quickly corrected his line once he realize I was there.
You have to be very aware, and take additional steps to ensure your visibility.