I really like the stuff.
As was previously stated it does take a little more screen wash to clean grime off.
I do find that bug splats don't seem as hard to remove and with decent rain (more than spitting) you don't need wipers at speeds above 35-40! Also ice doesn't form as easily.
A video I got my fiancee to take while I was driving up the M6 in a mental storm:
Please excuse the poor quality mobile phone capture (I don't think we could have chosen lighting to give the camera a harder time).
I think it makes the point though.