Thanks, will do - in particular because this time I also got Apple Care on the machine. Remaining problem is to actually get an appointment in the genius bar (I'm traveling a bit these days, and they tend to booked out here for a week in advance).
I'm really curious as to the WiFi thing - I'm definitely not the only one with the problem (see my post here https://news.ycombinator.com/item?id=13494910 with some links), but I haven't seen it widely reported at all.