Been a while since I've been over to the USA, but on the course of 5 years flew with AA, BA, KLM, and Virgin (twice). Some flights were to LAX, others to SFO.
With AA (first trip to USA) I went from Manchester to Chicago, and stayed there a few days (since I didn't want to just go direct to California and have no site of anywhere else).
Trans-Atlantic flight was fine, service and staff fine. Across USA from Chicago to LA was another story - nearly 4 hour flight with no on board entertainment at all. Not much to do once you've digested the airline magazine (lady next to me from Fresno had been on a course in Chicago, and as it was November, had caught flu, so talk was minimal!)
For KLM I went via Amsterdam, and facilities were better than BA, but only a few big screens to watch films, compared to individual screens on Virgin.
Trips with VA and BA were from Heathrow, Virgin had individual entertainment, hence second trip with them, even though they were about 50 quid more costly than BA, as I preferred the options.
Will be interested to read of other travellers comments over next couple of years, as the financial situation may cause a shake up of services.