Can we see a hat leaderboard for all SE users alongside the leaderboards of the sites?
This leaderboard is added with Winterbash 2013! You can see this here: The Stack Exchange Network - Network-wide leaderboard
In the leaderboard only unique hats are counted.
The feature requests that are coming in for Winter Bash, IMHO, should be status-declined. This is an event that's designed to be fun, and it's an event that is really only going to last for another 12 days, then it will be over.
I've encountered some bugs, but I've not reported them because there isn't really a point in fixing something that will be gone shortly after the New Year. In addition, as Laura mentions, most of the team is on vacation and won't be available.
Aside from that, there's really no guarantee that this same event would be held next season either, which makes this, and any other Winter Bash request, an extremely low priority.
There are many other feature-requests yet to be implemented that will have a positive effect on the network year-round, and we should focus on those instead. For instance, we could focus on ways to make it clear how to improve a question to reopen it, which would be helpful for many users who don't frequent meta.