Aero Wheels, Velocity Wheels. Does it really matter? Of course, they look pretty. But what I do not understand is: How will having taller rims or  composite wheels improve a ride? Is the increase in efficiency drastic enough to make you think twice while changing rims? Or is it really not that necessary with the cash it demands, for a tiny bit of improvement? 

PS: I tried to find out about this on the internet, but I have found bulky articles about them, so frankly I didn't read them and decided to ask here.
Given graphs like the first one on this page, which show how steeply wind resistance increases with speed, I take it that small changes in shape can be relatively important/effective at high speeds (and not at relatively low speeds).

E.g. my top speed when commuting is about 30 kph; the tour de France speeds on the flat are more like 50 kph. The power required to overcome wind resistance at 50 kph is more than triple that required at 30 kph.

It's also relatively important/effective if and only if you've already improved/maximised everything else (e.g. the rider's position and clothing).