As someone actually affected by this - when I went from my iPhone 5 to a Samsung Note 3, I noticed that all of my family and most of my friends (iPhone users) would receive my text messages but I would never get theirs, ever. Yes, I turned off iMessage on my iPhone, I de-registered my account via iCloud settings - waited 48 hours. Did that help? No. Two weeks later, I was still having problems getting text messages from family/friends/iPhone users UNLESS they turned on the (off by default) send as SMS if iMessage fails. But, I realized any iPhone user that I hadn't told to do this yet wouldn't be able to text me.
So I changed my phone number. Solved that problem. Yeah, it was a bit inconvenient but to be honest, I wanted a different area code so it didn't bother me too much.
After my Note 3 I went back to Apple with the 6+. When Apple finally acknowledged the problem - I helped at least two people I know that went Android from iOS solve the problem with that website Apple put out (lucky them!).
One of them went back to Apple like I did too.
It didn't cost me anything to change my phone number with Verizon Wireless. Sure, it was a little inconvenient but I'm not sure how you could sue. Was it right? Meh, iMessage is pretty cool and no product is 100% perfect.