Mark UK

The cost of living, chavs, the outrageous house prices, chavs, the impending house market/economic crash that is inevitable due to the fact that the economy is entirely service-based and house prices are vastly beyond the reach of the average wage earner, chavs, city centres on a weekend night (because of chavs), chavs, the tabloid newspapers and that idiot culture that they spawn (chavs), chavs, xenophobia, chavs, money making speed cameras, chavs, the crowds (of chavs), the Middle England mentality, chavs, NIMBY, chavs, petrol prices, chavs, VAT, chavs, the fact that restaurants charge you for a refill.
And chavs.

I emigrated to the States because my wife (then fiancee) had kids and it would have been much harder for her to leave her family behind than it was for me. Also, I had moved abroad twice before (both times to France) and already went through the pains, etc. The first time was definitely the hardest by a long way (not to say the other times weren't).
Of course, an ocean between you and your family is a lot scarier than having just a channel between you.
The cost of living over here is a lot cheaper - something you'll appreciate when you visit the UK as a tourist. As a tourist to the US, everything's so cheap, it's amazing. As a tourist to the UK, everything's so expensive, you worry incessantly about having the cash to enjoy yourself.
The job market sucks in the US right now, but with the resources the country has, it has more of a chance to improve than the UK does, IMHO. Personally, it was a no brainer. As much as I miss my family, friends and football, I definitely made the right decision.
It's a big jump - I'd hang fire on doing it until I was CERTAIN it was the right thing to do. I really wanted to move to the US and I still went through the usual adjustment pains, etc. Whereas I don't place quite the emphasis on where I live as Brother Hesekiel (I live in a place I don't particularly like and would much rather live in North Carolina but we can't move just yet due to family reasons), it is important that you're both willing to live in a place and one of you isn't there somewhat begrudgingly.
(As a tangent, I do agree entirely with Brother Hesekiel about the South of France. I loved living in the Cote d'Azur. The brilliant azure water in the foreground and the Alps in the background - amazing).

Thanks for the info. I maintained my bank account in the UK, but, sadly, I don't have $10,000 in it. More like $10!