Honestly, I've seen them in rest stops and didn't get a very high impression of them. My Boss wanted to put them in during our last renovation and I talked him out of it for various reasons.
1 - As elhigh said, the liquid barrier adds maintenance.
2 - The urinal, compared to the sinks and toilets, already uses the least amount of water in the room.
3 - Even with water, we already get calcium buildup in the traps. This would make it worse!
4 - Without water rinsing the urine off of the fixture, the smell and bacteria would be out of control.
I view them as unsanitary and I just think that your money could be better used in other upgrades to your restroom.
As far as "corrosiveness" goes, "There was a post on BuildingGreen.com's blog by Alex Wilson in 2010 about waterless urinals where he mentions that uric acid salts can form in the pipes. But, if the owner takes the time to flush a larger amount of water down the drain from time to time to wash away the salts, this problem can be avoided."
If I have to dump a bucket of water down the drain on a regular basis, it's not waterless! So, what's the point of having it?
Also, it depends on what type of pipes you have. Copper drain pipes would certainly be the worst while PVC would be the best.