My concern about having the `~>` is that after `4.1` is out, a bundle update would update it. And that could bring regression/api changes.
Also the `~>` sometimes hides versions, lets say if there was another gem that requires `AR <= 4.0.3` the `bundle update` would never go over that, nor complain about it.
That said I am a huge fan of `~>`, but for core gems, like activesupport and activerecord, I try to force a version for them.

Thoughts?