I think you definitely have to go in with your eyes open. Being a foreigner is pretty difficult sometimes, you're always watching what other mums are doing to fit in and make sure your kids don't miss out, and you have so many hurdles to jump before you can even start work or see a GP.
It also takes time to settle somewhere- don't expect to feel at home in the country for the first three years or so. Then it starts to shift, and by ten years you'll find you have lost touch with home so much more that the new country is definitely your REAL home - by losing touch I mean with the culture, like the in jokes, minor celebrities, what they're all watching on television etc. The internet helps a lot with that though, but the time difference is hard.
I would go in a heartbeat BUT for me it makes sense: I have family in three Australian states and have been several times, and I'm not British anyway so even though I've been here my whole adult life, I'm used to being slightly foreign and having to work harder to find out what to do for children, work etc. I come from a country that has a health insurance system so it wouldn't particularly bother me to go back to that, although I've deeply appreciated having my babies on the NHS.
If DH would ever consider it I would go, even though my career is just taking off and it would probably hurt me professionally. And I'd still mourn not being able to go back for the weddings, funerals, milestone birthdays, new babies of the people I love. It's just so far.