I have an oil pan heater installed in my A3 and like most I don't notice much of a difference with starting at all however it just hit -32c here and I am noticing the transmission is shifting faster/smoother with the heater in use.

 

I've now had by A4 B8 almost 2 years and still do not have a block heater. So far I haven't missed it despite having a few -40c days here in Regina with the Audi parked outside.

My only concern is that operating a vehicle when it's that cold can't be good for it - although, so far, no problems. As AudiGood mentioned, the transmission in my non-block heated vehicle is stiffer for the first few km's after I leave work at the end of the day. Generally, the A4 is parked in the garage at home - so it's not hard to live without the block heater.