HollyBolly the prime motivation for DH moving to SF was financial - the choice was move over there (and potentially make a large pot of money) or stay in UK and be unemployed - in the midst of a recession. So it was a no-brainer.
Originally thought it was going to be just a year, has now been 16 months but he has promised he will come back at Easter, regardless, because we have all had enough of him being away. Hasn't worked out as well financially as hoped but has been OK.
Luckily he has been working for a UK company so gets UK holidays, and has an understanding boss who recognises the sacrifice he's making. He was back in the UK I think 4 times last year, was home for a month for both Christmases. We spent the whole Easter holidays (4 weeks, slightly extended thanks to Volcano) and 3 weeks there in CA in the summer, and had a great time - DH lives in a v comfy bachelor pad in downtown SF which is great. I took the dc to new york for a few days too so i think they have benefited culturally from the travelling (although not mad about american culture myself).
Cons are: Time difference of 8 hours can be awkward for communication, he often wants to Skype at annoying times.
He misses us a lot at weekends, during week we're both too busy to notice, although its not too bad as he has some close family out there.
when he comes home he is jetlagged for the first week of the trip - asleep when we are awake and vice versa.
He has put on over a stone in a year, because he eats out or takeaway most of the time!
I am finding I miss him more as time goes on, and also feel resentful that I have to bear the full brunt of parenting. Particularly since September when DS1 started secondary school so I have 2 school runs to do.
The dc get very upset every time he has to leave (although they seem to get over it quite quickly and settle back into the different routine).
My social life is rubbish when he's away - the invitations to dinner parties etc disappear when you are effectively single. I have to work hard to do things with other families with an absent dh.
But as I work I have to spend most of the weekend catching up on domestic chores anyway - and the dc get a bit neglected.
I have had to deal with quite a lot of big domestic issues while he has been away, e.g major central heating breakdown during cold snap, and while he has been supportive its not the same as having him there.
Logistics are much harder with only 1 adult in the house - dc have to come everywhere with me (although ds1 almost old enough now to be left alone).
Hope that helps HollyBolly - I think the age of your children is critical when making decisions like this.