After reading about how many players do not levy CS units I wanted to come in here and ask the bigger question.
Do you build IZ's, Dams and Canals?
I rarely do this.
Many games I don't build one IZ as I usually take them.
I have played around with them a few games where I was able to get 200 or 300 production but I still just stick with Campus, Commercial Hub and Theater Squares as my go to for just about every city.
I was going to make a separate thread but I think the IZ question goes along with the Canal Thread.
I definitely build a lot of IZ's, production seems so important to me for anything really, and since I always play Marathon it feels like it really gets things going. I haven't done the maths if it's really worthwhile, but I also find it provides you with GE points and some of them are really interesting to get (get the Mausoleum as @Disgustipated said and it's one extra charge, that will get you to the Moon AND Mars in two turns!).