They look great. The seat is really easy to take on and off, so I can keep that solo look when the wife doesnt ride with me. The back rest is a bit more tricky, so I'll probably only put that on when we do longer rides.
The Mustang passenger seat does fit the stock seat (even though Mustang will tell you it wont). It's a great looking passenger seat. The one HD offers is way too bulky for the Nightster in my opinion.
I'll get some pics up shortly.