Totally agree that having to hold down the "R" key to select a range has ruined my workflow and train of thought. It was a step backward in usability. It makes absolutely no sense to throw another step into the most basic creative process which is selecting pieces of a clip to actually use in the movie. I'm very upset about this change because it makes no sense. I really hoped the software engineers see how unpopular this change is and revert back or give the user a preference as to how they want to select a range. I cannot imagine any user thinking, "Wow, this process of holding down the 'R' key is really a nice update. It actually makes iMovie easier to use."
Essentially, the iMovie team reversed our normal workflow. Previously, you double-clicked a clip to select it. Now, you click on it and the entire thing is highlighted. I found it so frustrating, that I deleted 10.1.2 and grabbed 10.1.1 from Time Machine. I'm back in business with the wonderful 10.1.1.
You can send feedback to Apple at: http://www.apple.com/feedback/
NOTE: If you choose to revert back to 10.1.1, use App Delete to remove 10.1.2 as it will remove all of the preferences and other bits of iMovie scattered around your hard drive. Simply dragging it into the trash will not work. I tried this first and was able to get 10.1.1 running again, but, strangely, it was missing a part of the top toolbar. I then used App Delete, reinstalled 10.1.1, and everything was perfect! It gives you a fresh install as if you're opening iMovie for the first time.
Also, installing the 10.1.2 update will change your existing iMovie Library files to only be compatible with 10.1.2. They can't be opened with 10.1.1. I solved this by simply trashing those libraries and restoring my previous ones from Time Machine.