Interesting to hear all the opinions. I will definitely see if I can hunt down that AIBU thread.
Background: DS is 3.6, will be increasing nursery hours to full time from June when I start my new job. It's my first step back into employment in 5 yrs and I beat loads of other candidates to get it. It's very important to me.
DH starts his new job in Aug. He's been working all his adult life for this role, and he totally deserves it. His current job means that DS only sees him for about 5 mins in the morning, and he's frequently already in bed when DH gets home, so I dont think he'll be massively impacted by the commute.
The biggest change will be for us as a couple. We are going to Skype every night, and part of me feels like we might actually have more meaningful conversations than we do now as at the mo, we tend to chat during dinner and then just slob out in front of the TV, 
We intend to enable our weekends as much as possible by getting a cleaner and dish washer, and also have babysitter lined up for the nights when i want to meet up with people during the week.
Not too worried about the commute tiring DH out as it's actually not far- only 1.5hrs. It's just that the nature of the jobs requires that he live on site or in the immediate vicinity.
There are a few reasons neither of us want me and DS to move with him. Firstly is the issue of my job. It took me 6 months to find it and I dont want to let it go after such a fight for it, especially when it is my opportunity to move back into employment. Secondly, we are very close to my parents where we are now and they see DS at least once a week. We feel it would be cruel to take him away when they have such a close bond, not to mention the fact that they're a great support network. Thirdly, we've been able to afford a really nice house where we are now, and if we moved to the immediate vicinity of DH's work, we'll have to massively downsize or completely overstretch ourselves financially to live in an area that just isn't as nice as where we are now. We all also have close friendships here which we'd be sad to leave behind.
Sorry, that's a really long post, I dont blame you if you don't get to the end of of
it!!