Except you only get the version that was released at the
beginning of the cycle. In other words, when your subscription is over, you have to downgrade to a version that's a year old. Bugs and all.
With most software, this would not really be a huge deal. Photoshop? Who cares. Excel? Meh.
But with Jetbrains products you've got to consider whether the old version is going to be 100% compatible with your existing project files, plugins, keybindings, settings and configurations.
It's quite a gamble IMHO.
