I didn't sell my company to MSFT but I imagine it is the same. There will be a period where everything is great and you feel like you have freedom then that will end and you will be at their whims.

My advice is: day-one stop thinking about it as your company and stop caring. Do what needs to be done to help your employees and to make the transition to MSFT a good one and then leave. I lost a great deal of money because I cared and stay around. If I had sold my stock at the first chance I could and left I'd be a millionaire many time over. I lost it all because I made dumb decisions that involved caring about my company when it wasn't mine anymore..