For us, as plugin developers, this is a nice move as it opens up more market for us.

But if I were a developer of strictly FREE plugins, with zero premiums or stuff to sell, I'd feel completely cheated at this point. WordPress.com starts making money off of a free plugin. The developer doesn't make money from her or his plugin. Only Automattic makes money off of their work.

Does this bother no one else?

Developer X makes a free plugin, which brings great add-ons to wordpress. Developer X makes zero money off of this plugin, because Dev X doesn't sell premiums, support packages, etc. Automattic, however, takes Dev X's plugin and they make money from it.

A lot of people will buy the Business Plan now because of the 3rd party plugins.

Again, for me: this is perfect. I'll have more people (paying people) who will install my freemiums, and they'll end up also buying something from me. Which is cool.

For the dedicated devs who just wanted to offer something cool for free, I'm not sure this will seem like a fair move on Automattic's part.