Last time I was in Havana in November the lines were long at the cadecas and banks. Does anyone know how the Havana airport currency exchange booth compares with in-town cadecas as far as rates?

It depends on what currency you are changing.
Dollars are a fixed rate; other currency fluctuates slightly, maybe a penny difference for Euros.
In town less lines,but you really should try to get the black market rate of .95 CUC to $1 USD with C notes preferred and possibly through your casa owner. I will never exchange money through the government again and get screwed.
I don't know,can't imagine why since there isn't an added 10% penalty to the3% fee on the exchange as there is with USD.
I have never heard of any black market rate for euros.
As YB says, the Cadeca margin is only 3% anyway, and there isn't the same demand for euros in Cuba.

There is a reason why there is a 10% additional spread on USD paper in Cuba. Hence, the black market.
No such thing on other currencies, hence, no black market unless someone is trying to screw you.