Earlier this summer I was heading toward Bryant Park to catch The Maltese Falcon. I'd heard that these new subway trains were going to be rolled out shortly, but had yet to see one. (Years ago, as mentioned by sockpuppet, I'd seen one of the test cars at 34th Street, on the E line. Sadly, I was late for work and the train was heading uptown so I couldn't hop on as I so wanted to.)
As we pulled in to the Brooklyn Bridge station on the 4 line, I saw one of the newer trains on the local track. I immediately transferred, even though the trip would be longer. Much to my surprise it was the first of the new trains! Several news people with cameras and such were in the next car, interviewing riders about the redisgn. But that was what impressed me most, off the bat - the windows between cars! In the older trains, you could only peer into the next car through a small window in the door that leads between cars. The newer models include windows on either side of this door, allowing a clear line of sight and making the train feel more spacious.

Otherwise, everything was as mentioned above. As a frequent rider of the 4/5/6 line, I hope to more of them soon - to date I've only been on them twice. That initial ride, and then, more recently I rode on one of the special Subway Series cars on the 4 line. It too was of the new design, but plastered with Yankees' and Mets' logos - much better than the aforementioned Dr. Zizmor though a bit overdone. :)