Hi Deanna! Welcome to the board! My husband and I moved here in September. We live in Bloomsbury, which is near the British Museum.
Living in London is a great cultural experience. We have no regrets about making the move, because we wanted to have the experience of living abroad and travel more extensively in europe. We love Great Britain in general. There is so much history here. It's great to be so close to Europe and we're enjoying every minute of that.

Yes, it is very expensive to live here. I am not sure what you are interested in, but a flat will be pricey anywhere that's nice or convenient. I feel it is far better to live closer to your work/college and pay the extra money and walk to school/work. You heard right about the underground, it is expensive and unreliable. Everyone I've talked to at work hates it, but uses it anyway. You may end up paying less outside of London (and get a bigger place in a quiet neighborhood), but you will pay the difference in travel into work. The tube has a website with prices of monthly travel cards by zone. It is difficult to know how much you'd pay by train, not knowing where you'd be settled. My guess is your college may have a department which would help you find accommodation. That would probably be your best option. I don't know if you'd consider a flat share, but many people/couples do that here to save money. The apartments here are very small and certainly not what we're used to in the states (unless you pay considerably more).
I feel that your friends won't have much problem finding a job in IT here. In fact, there are not many who can obtain a work permit, but people who are in upper management, IT and healthcare workers (doctors, nurses & specialized techs) can get one. If you obtain a work permit, your spouse can work under your permit. If you go to the forum section, I and others have posted some info about obtaining one. I got my job through a recruitment agency on the web for medical techs/doctors & nurses. They obtain the work permit for you. You must obtain the one for your spouse yourself. The web might be a good place for them to surf and look for recruitment companies.
I have found the people I work with are the friendliest bunch of people I have ever worked with. I was made to feel most welcome on the very first day. I think people are curious about Americans, they think they're all like people on Friends or whatever. They are very social people and like to hang out after work (at the pub or wherever).
It's very true though, George W. Bush, is not very popular here at the moment. (He is not popular with me, either, so I before I voiced my opinion, people were very polite and did not make comments around me). I think some of the stigma attached to Americans comes from some of the American tourists to London. I have seen on numerous occasions, extremely rude, obnoxious and insulting Americans (and "America is biggest & best and you are all backwards here, etc" attitude). For some British people, these are the only Americans they ever meet and I don't blame them for getting the wrong idea, actually. It's just like anywhere, if you're nice, most people are nice back.
Let me know if there's anything about London you'd like to know. There are so many little hints and pointers you can get from this site. It sure helped us! I hope I can be of some help to you!
-Caroline