Going on from what others have written: K2 battery life is low for bike computers, no doubt about it. But it is plenty for most and I think that's the reasoning behind Hammerhead's rationale. I'm happy to trade battery life for the superior res screen. That's the choice they have given us vs Garmin et al.
I do 20-24h training weeks, typically my longest rides are around 6-7 hrs and even at maximum screen res, my K2 has managed with 20%+ left over - hooked up to a PM, Sram electronics etc. I think the K2 from my own experience is good for 10hrs+ if screen res is managed. I'm in the habit of charging my K2 after every ride; the charger is next to my bikes so part of my post-ride routine. I guess if folks want to only remember to do that once a week then they need a Garmin.
I have friends doing a 5 day tour across the country now but they stay in hotels each night and can recharge batteries. The Garmin devices are excellent but their battery life is only an advantage for those doing rides longer than 10-12hrs or tours with no recharging available; that can't be a massive segment of the market. For me, the K2 is good for 300km.
As for the rest, Garmin leads the back-end software for training etc if that's of interest but the devices themselves don't excite me as much as the K2. Hammerhead are upgrading their device 2x a month and have been since launch. Give it another year and and it could well be comfortably ahead of all its competition for everything bar battery life. As it is now, I don't see the 1040 as being much better really and it costs a lot more. It's only real advantage is battery life for those who need the extra.
