Courage to choose
This topic about changing jobs after GC is near and dear to me. I am a husband of a doctor who had to go through 3 year waiver with sponsoring employer, in order to apply for a green card. After 3 years of waiver she applied for green card and got it some 9 months later. Hooray!
The problem was, employer was abusive and manipulative, he really took advantage of indentured position my wife was in. It would take too much space here to describe all the ways and it really doesn't matter from the legal point of view. What matters is she prevailed and we have a green card now.
Of course, she wants to change a job. So, we hired a reputable immigration lawyer (not the one who got us a GC, as he stated that, since he technically represented both employer and employee, has a "conflict of interest") to advice us on this matter. The question was, how soon can my wife split from her employer after getting GC? Is it 30 days, is it 3 months, 6 months, a year? Mind you, we read countless threads dedicated to this question, no one has definitive answer as this is a grey area.
This is what our immigration attorney told us: The moment you get your GC you are free to split from your employer, either to get another job or to start working for yourself. You do not have any obligations to your sponsoring employer after you get GC. Green Card gives you unrestricted right to live and work in the USA. As to the pertinent question of intent, she has about 20+ years of experience and spoke many times with immigration officers. She told us that if USCIS wants to revoke your GC (let's say your vengeful ex-employer reports you to USCIS, and they decide to investigate) they would have to prove to the judge that you had prior intention to leave your job when you get GC. This is VERY difficult and USCIS knows that they would lose majority of these cases, therefore they do not want to waste their resources in order to win tiny majority of these cases, probably less then 10%. Therefore, they routinely ignore this matter.
Again, this is just an opinion, albeit educated one. Life is full of risks in general, and when it comes to the legal questions in particular, but, in this grey area, you really have to decide for yourself, there is no definitive answer. It helps to know different opinions (as this one differs from many others, especially from Rajiv's one). One has to have courage to to trust in oneself and do what is BEST, not necessarily what is least risky.