This is a little off-topic, but a couple of former brewers for Goose Island are starting their own 40-bbl brewery in Geneva, IL, shortly. http://www.penrosebrewing.com/
I've heard that they are bringing a few other Goose Island employees with them.
I think there's been a bit of a diaspora since the ownership change, though I think to some degree there were always people leaking out to other local breweries. This is good for the local craft beer scene. I'm not sure if the rate has increased, but I bet it has.
I think you're right about GI employees fanning out to other breweries. Besides Tom and Eric who are starting Penrose, I met a former GI sales rep who now works for Summit last month who said that GI lost approximately 40% of its workforce (voluntarily migration) after AB In-Bev took over.
I have no opinion on GI beer since the AB In-Bev purchase because I really haven't had too much GI beer, even before the buyout. But I can tell you that when I met Tom and Eric at this year's Craft Brewer's Conference, they were super cool guys and I am genuinely excited about their brewery. I have relatives in Geneva and I'll be making a trip there once Penrose opens its doors.