0.11->0.12 totally hosed me. Not necessarily because of TF itself, but because of the scaleway provider I was using changed everything around such that coming up with the right state file that didn't destroy all my existing instances, was very difficult. I eventually gave up and found someone to do my hosting for me cause it was just too much work to deal with TF changes over time.
I also feel like the concept of looping is a weird afterthought. I want to create 10 vms of the exact same type. Now I have to build a module for reusability, remember to put count everywhere and use dynamic variables all over the place, after studying all the documentation 1000 times. I wish this had been thought out a bit more.