It's free. FREE. Free costs money. Give me a break. I use Dropbox & Evernote free tier. I can't complain about the limits, either I pay up or shut up and use it or find an alternative.
The problem isn't having limits on the free tier. The problem is changing the services for existing accounts (free or otherwise), in this case to completely cripple free accounts. I wouldn't even complain if they only applied the 3-device restriction to new free accounts