So far, I'm on my third Band1... the metal on the charging connector, as well as the sensor cluster on the clasp, corrode and create raised bubbles that prevent the band from charging - a pretty common occurrence, from what I've read. This happens even though I've taken exquisite care of the device: wiping it off with a clean, slightly damp microfiber cloth every time after a workout and before charging in the morning, making sure to give the metal parts a bit of a scrub to clean off any sweat or buildup. Already, after only 6 weeks, #3 is starting to show small bubbles and discoloration.
I bought Complete as part of my initial purchase (early January 2015) for $20. Each return to the MS Store has been covered by standard warranty, so my Complete coverage should still be intact. My first exchange was swapped out with a refurb, and the last one was swapped out for new. With each exchange, I waited for nearly an hour for them to figure out how to process the exchange.
I had a bad experience handling my wife's 1st gen Surface Pro Complete exchange at this MS store, and I have a bad feeling that I'll get a similar runaround when this Band inevitably fails. I'd like to think this should fall under some sort of "lemon law" and my 3rd exchange should be for a different product or refund, but that depends on your local consumer laws.
TLDR; It depends on your MS Store. I happen to live next to a terrible one, and policies seem to change based on the mood of the manager-on-duty. Since it looks like they'll sell Band1 next to Band2 for at least a little while, I wouldn't bank on getting an upgrade deal.