I have to admit, I'm quite happy with my flexible 35 hours a week. Technically, quite often it floats between 34 and 38 hours, due to the flexi-time aspect, and as long as the work is done, no-one really cares about the exact amount of time spent working (as long as it's within reasonable slips either way).
However, there have been a few interesting conversations with some of the middle-management types. Technically, yes they get a lot more money annually then I do, but when you look into how most of them end up working a lot more hours over the "official" time. So it actually breaks down to them earning simililar, or even less per hour than I do. Of course, they then get bigger bonuses at the end of the year, and that probably makes up for it.