I posted a trip report about BHX-DUB-NYC last year. It was brilliant - as an 'alien' it took maybe 30 mins to get through US immigration at Dublin.
What's more, the airline staff are on top of this.
If you're using two tickets etc then it might get messy, but I thought it was a brilliant set up.
http://www.flyertalk.com/forum/archive/t-1341451.html