As regards the above, thought I'd put my thoughts down:
Expensive - yes, they are expensive and increasing each year. Saying there's 'no single supplement' should be removed as we're obviously paying a premium for having a room of our own. On the plus side, both holidays I've done this year have been well worth the money, hotels, food and trips brilliant. However, I'm noticing more options creeping in, this alongside the additional costs of connecting flights and overnight stays in hotels near Heathrow/Gatwick pushes the price up even more. As long as JY maintain the quality they offer now I'm quite happy to pay, although I may have to do less holidays in future if prices keep going up.
Seat Rotation - I prefer to sit near the back and have a seat to myself if possible and let whoever wants to sit at the front do so, sometimes they may be travel sick or less mobile than me. I think at the end of the day we should all be adult enough to be able to sort it out amicably and I've never had a seat rotation policy on any of the 7 JY holidays I've done to date.
I'd say the most important thing for me is to have a decent tour rep, I think this can make or break a holiday. After having one bad experience I'd hate for that to happen again. I think it's more important on a JY holiday than on any other as everyone is travelling on their own and some people need more help than others. If the tour rep is very knowledgeable, and really enjoys their job and the area they tour, then it makes the holiday much more interesting.