I have installed quite a few in boats, But have not had the occasion to install any in a bus yet.
I have the Magnum Opus [non vaccu flush] model in my bus and it's quite nice..
I assume you want to know how the vaccu- flush holds up? or do you want to know how it works?
Pro's, You can install the toilet up to 20 feet away from the tanks. They only use 1 pint of water.
Con's, On the pricy side, takes alot of planning to layout the installation
Here is the link to SeaLand/Dometic info on Vaccu-flush http://www.dometicsanitation.com/vf.asp
Hope this helps