Here are Stereophile's measurements from their review of the Aon 2. The tweeter has a reasonably conventional dispersion pattern, not too different from a 1" dome. However there is a bit of suckout vertically at the crossover point, but not laterally. As for frequency extension, this tweeter is down only 5dB at 30 Khz and there is no 25 Khz oil can resonance so typical of an aluminum dome.
Folded ribbon tweeter might be somewhat directional compared to some others and is very polite in a good way, ie easy on the ear. Might take some getting used to if one is used to more bite in the high end as may be more common with other tweeter types, like soft dome, etc.
You are right, the tweeter is uncommonly smooth, especially taking its speed and extension into account. I think it's because this design doesn't suffer from ringing, resonances, and overshoot typical of a dynamic tweeter. The folded ribbon has a much larger surface area (about 7 sq. inches), so the diaphragm doesn't have to work or extend nearly as far as a 1" dome (.78 sq. in.) to reach the same SPL. Several reviews have noted this and attribute the combination of frequency extension and smoothness to this lack of the inertial artifacts we've become so accustomed to hearing with 1" circular (esp. domes and inverted domes) tweeters.
I heard the Aon 3s and was very impressed; their fullness sounded very much like what a mid-sized (10x12 footprint, 40" tall) tower typically produces. And then there's that very smooth, natural treble.
OTOH, I'm also seriously considering the SVS Ultra Towers for my LP-sourced 2-channel system. From all reviews I've read, the aluminum dome tweeter of that design is very smooth and evenly distributed thanks to its ferrite magnet, damping, and waveguide.