That is so true,
my wife had a problem in a very small (~300-350 sqf) apartment she rented. When I carefully installed some foam/polyurethane self stick cords around the window frame and the door frame, we truly FELT the difference in temp around the room. We also had a noticeable difference in the sound coming from the street.

We used something with a "P" profile, similar to that:



Those electric radiators with oil inside do wonders (albeit in very small spaces, like the isolated 15x17 room Zuki talks about).

[This message has been edited by trident (edited 11-12-2008).]