I had the chance to apply for a green card (just got PERM certified) but have decided that now's a good time to take a break from the valley instead. The biggest feeling of relief is that I can now take a job that isn't my primary employer (!!), found a company, build things and not face deportation as a result. It's been 6 years since I last had that opportunity -- and doing it in the US is at least a year away. Not dealing with US immigration is worth not having a concrete plan :)
Like the OP I'm also an EU [and Canadian] citizen, so I'm not lacking for places to go. Beyond those, there are so many countries that actually welcome people looking to build with open arms.
Like the OP, I'm sure I'll be back someday. For all it's faults, it's still Silicon Valley.