Update: invitation received Nexus 6 & Fi welcome kit ordered
Like some others in this thread, I received my invitation last night and ordered a Nexus 6 & a welcome kit for arrival next week.
I am looking forward to porting my service from T Mobile (which has worked well) to project Fi and with any luck will have it active in time for my next international travel. As a very light user of cellular data I expect my bill to be cut in half from $60 to $30 or less a month.