Quick Stats for me:
Keys Acquired
Quest Keys: 2,774 (83 quests completed)
Daily Gift Keys: 525 (21 days * 25 keys)
Reward Keys: 250 (from completing 45 total quests)
Pickup Keys: 528
Total Keys Acquired: 4098
Key Usage
Boxes Opened: 91 (5 rounds where I opened all 16, 1 round where I opened 11 and reshuffled).
Shuffles Used: 1
Keys Spent: 2,320 ((91 * 25) + 45)
Current Keys: 1,778
Expected Keys Remaining
Remaining Quest Keys: 526
Remaining Daily Gift Keys: 300
Remaining Pickup Keys: 300 (averaging 25 per day so far, with 12 days to go)
Total Keys Remaining: 1126
Total Remaining + Current: 2,904
Prizes Earned
Gifts: 118 (79 from opening non-gift boxes, 39 as the reward for opening the box)
Grand Prizes: 5 (3 owls, 2 other, 18/20 on the 6th)
Daily Prizes: 7 Elvenade Logistics Centers (I only used keys on Day 21 of the event, and got a single 2x on the daily)
Buildings: Frozen Blue Flame x3, Winter Shrine x2, Frozen Unicorn x1, Frozen Orange Flame x1, Winter Forest Shrine x1, Candy Cane Unicorn x1, Frozen Green Flame x1, Snow Sculpture x2
KP: 52
Units: 10 Mages x2, 5 Heavy Ranged x3, 5 Heavy Melee x2, 5 Light Ranged x2, 5 Mages x4, 5 Light Infantry x2,
Instants: I failed to track this properly, but I got several low levelcoin rains/supply windfalls/ancient knowledges
Relics: Didn't track this at all.
Overall Feelings
My approach here was pretty simple -- open boxes until I've gotten the daily prize + all of the gift boxes. If I got the daily prize + all gift boxes early (and by early I mean, there were at least 3-4 boxes left to be open), I would use a reshuffle; otherwise, if there were only a few boxes left, I would open them to get the automatic reshuffle. I did get a little lucky with the timing of the Reveal 2 and Double Rewards -- they always came up when I was near the end of a board -- and I did get Reveal 2 to reveal Gifts once and Daily once, so that was nice.
As you can see from the fact that I only used 1 reshuffle, I didn't get particularly lucky with my box openings. Of the 6 total rounds I went through, I opened the last Gifts or the daily prize in one of the final 3 boxes 4 times. One time, it was on the 11th box I opened, so I used the reshuffle. it was the 4th to last box, but I chose to spent 75 keys opening 3 boxes instead of 45 keys to reshuffle (because I knew there was a 5kp reward in there, so 3 gifts + 5kp + reshuffle seemed better than spending 45 keys for a reshuffle alone).
I hope I get a bit luckier on box openings for my next round (which I'll be doing on the Frozen Owl Cave day), but overall, I'm quite happy with this event. I have a lot of keys remaining, and based on my average of 19.66 keys per Gift, I should get another 148 Gifts over my remaining keys. If those numbers hold true, I'll get 8 more Grand Prizes, which will mean 4 more Owl artifacts, which will guarantee me a Stage 10 Owl even without an FA. I've also averaged a Daily Prize every 331 keys, which means I can expect another 8.77 daily prizes, for a grand total of 15 daily prizes. Given that I got relatively unlucky in my box openings in the first round, I don't expect those numbers to go down any, but they might go up a tick, so that could be even better.
TL;DR: I like the event. Getting lots of prizes is fun. Guaranteed dailies is very cool too, especially when there are individual prizes you want that will help your city a lot. It feels like I'm playing a scratch-off game where I know I'm going to win every time, it's just a matter of when/how much.