I went to the Project Loon event today (Sunday June 16) at the Air Force Museum in Wigram, Christchurch, New Zealand. Here's what I learned. (Some of this may be misunderstood or misremembered, so don't take it as absolute truth, and this is all early prototype stuff anyway.)

It was quite a big museum-style exhibit with lots of people (it had been on the news), and several members of the team were there answering questions.

Currently there are four balloons up. Several have recently been successfully been brought down and recovered from the ocean (land landings are easier to recover but there is no nearby land east of here). The main reasons for testing here are that the stratospheric winds are "boring" (basically all west-east) and this latitude has few countries to coordinate with (they're working with Chile and Argentina).

The project involves a "couple of dozen" people and has taken two years to go from "ideas on a chalkboard" to this.

One of the balloons was there, inflated to its maximum size (launch size is smaller because of pressure differences, but it's a superpressure balloon with a maximum size). It was roughly 5m high and 12m in diameter. It has an upper portion with helium and a lower portion with air, with an impeller that can change the pressure in the air part, and thus control the height. The height control is used to navigate, by moving to layers with different wind directions and speeds, and can take it right down to the ground (though that sounds a bit untested). They are aiming for flights of "hundreds of days".

(continued in comments)