I doubt this is what the long term plan is. Apple forces you to jump through hoops to beta test stuff. But obviously this is in a much more Microsoft way.

I'll reserve judgement until I see how the public version is done.

You can use Bing in Firefox, I use both DDG and Google in FF. I could add one for Bing.

Looks like they will be supporting Chrome at some point, based on the announce event reports, one of the spokespeople said "Chrome has to implement some features" before they can support it, maybe they'll make a Chrome extension to fill the gap and get it working on there.