One of my strategies involves grabbing the sensor techs all in 1 research rush, and then buying an Eyes of the Universe, so I don't have to put sensors on my ships. With 4.0 yesterday, I did this, and then was going through my ships clicking on them (you have to do this in order to get the expanded sensor range immediately) I had a couple fleets formed, but when I clicked on them, the sensor range didn't change. In order to get the expanded sensor range, I had to disband the fleets and then reform them. Saving and reloading, or simply hitting the turn button gives the fleets full sensor range, but it's better if it worked properly (it used to) to be able to react to anything newly revealed.
Also, I had a few occurances of 'sensor ghosts'. An example of what I mean by that is: I have a ship I call Interceptor. Quick fighter with 1 small weapon. I bought the Eyes, and clicked on the ship. The sensor range expanded to 15. I advanced the turn, and the fighter went on it's merry way. However, at the spot the ship was when I bought the Eyes there remains an area clear of the fog, even though no ship remains near there.