Been lurking and re-living the anxiety from last year... Good luck to everyone! It is agonising. We accepted a place at T for 11+ and, to echo FarmerBarley, have been really impressed. The standard of teaching is excellent pretty much across the board and the school has a solid, well-implemented ethos. It IS hard work, and those boys coming from state schools will a significant step-up in expectations, but lessons seem to be made interesting and homework is varied.
A few things to mention about the interview. Do not imagine that it suddenly becomes a level playing field at interview. They still rank according to exam results and offer from the top, unless a boy comes across as completely unsuitable for the school at interview. They use some content questions (maths and English) to reassure themselves that boys have not been over-tutored in exam technique. If the school does make you an offer, they want you to choose them (they want a healthy acceptance rate from offers, and I think it is quite competitive between W and T), so they will go out of their way to make the whole exam experience / interview as pleasant as possible -- do not read too much into the manner of staff at interview.
My son was not asked which other exams he had sat, but the head in a very roundabout way managed to elicit information from us 'Is this the last interview he has this week?' type question. I don't think they record and use this information in making offers, but they do like to know what their competition is and get an insight into what motivates parental choice. This is one of the things that makes these schools so successful -- they listen carefully to answers from parents about 'what expectations do you have of a school for your son?'.
I know it's difficult, but try and keep a sense of perspective. If your son doesn't end up getting in, consider yourself as having won £14,000 on the lottery for the next seven years! Become an active parent in whatever state secondary your child gets into. Watch the news. Realise that not getting into independent school might seem like a tragedy of epic proportions at the time, but it is a minor setback in the big scheme of things.