haha, glad you liked it. It's actually the story i tell first when friends ask about the trip - a 'highlight'

i didn't actually try it backwards but when I saw the contraption that's what I thought of doing 

Yeah it was great, but being on my own it was high highs and low lows. The next time I want to go in the summer with a buddy.

In this case the S-Bend is below the water surface and runs under the seat. The S-bend will only prevent the odour from the canalization from creeping in, not prevent the odour from IT. That is what the air-ventilation does in the bathrooms (you probably did not see them).
In no toilets will the s-bend come above the water level as that would defeat it's purpose.

So even if you do not have the surface and IT takes a plunge, you will still have the the odour.

Should you ever have too much of IT, you can naturally just flush it down and continue.

Did I mention that my first job was as a technical draftsman for heating, air-ventilation and sanitation? Though I never thought THAT knowledge would be useful on a IT-themed board.

@teletubo:
The problem with plunging types was that regardless of the size of the job, you had to flush all of the water.
So even if it was just a no1, you will flush all of it.

Strange thing is, I know many people in the US that have plunging ones, yet tend to 'conserve' because they are not directly hooked up to the sewage and their tank would fill up faster if every job was flushed.

In Germany, many toilets already have 2 panels/steps to push, one for no1s and one for no2s. Plus you can stop the action at any time.
Also some even collect rain water to use for flushing.

You wanna know something really strange about Germany? The tap water in Germany is the tightest regulated and monitored water. Even more then anything you can buy.
And we use it to flush our toilets.
Though a typical German would actually buy bottled water, partially because we prefer the sparkling (carbonated) kind.