Well, in 2006 I used my bike almost every single day - pulling a bike trailer with two little children in it too (very good exercise and since I stopped doing this I've piled on the pounds a bit - see my thread on losing weight ).

One tip if you're looking for cheap but reasonable quality bike gear - Aldi. They have a range of stuff from "Crane Sports" which is quite good enough for normal use, I bought most of my clothing from them. They have some pretty good winter / cold weather gear which has good insulation but breathes so you don't end up sweating like a pig when wearing it. This range isn't always available at Aldi, look out for their special offers.
Personally I don't bother with the waterproof stuff since let's face it, if you're on a bike in the rain you will probably get wet, as long as you have enough clothes on and you're working at it on the bike you'll be warm enough. I wouldn't worry about getting wet but keeping warm is important.
As for commuting around Zürich, it depends a bit on where you are, living in Adliswil meant that it didn't make any difference which way I chose to ride, getting into Zürich meant going up a hill or two but you soon get used to that. There are plenty of bike lanes around but be aware that if you have a high quality road bike you'll probably prefer to use the road since some of the paths have poorer quality surfaces.

Have fun