As I get more comfortable with the system, some of its flaws start to stick out. I know a lot of people claimed the system was essentially Windows 8 because of the flat metro tile look, but the idea and function of the One UI is also essentially W8. This is evident when you realize that everything in the system is an app, which causes some annoyances but does have its perks.
The perks are that since everything is an app, this should make updating certain integral parts of the system very, very easy, which is good. The core OS is fine and while I'm sure we'll still see updates to it, we wouldn't have to wait for bi-yearly updates to get fixes to individual parts of the OS (assuming they would do it the same as the 360). With the console defaulted to "instant on" standby and automatic updates enabled, Microsoft can push out updates to almost anything on the system at any time and everybody is good to go. Whether they do this or not is anybody's guess, but surely they'll take advantage.
Where the "everything is an app" sucks is with things like your friends list and achievements. IMO, this stuff should be baked into the OS. When viewing achievements in-game, I don't really feel like I should be taken completely out and into another app. In the end, it's not much different since you can quick-resume back into the game, but it feels disconnected.
My two biggest issues at the moment are how the friends app works and that the achievements app is horrible. The following/followers thing sounds good on paper but I think the biggest issue is that you aren't told when somebody starts following you (at least this is what I've read, since nobody has started following me yet). For example, I started following purbeast and can see all his entries in the activity feed, however he hasn't started following me back. Now, I'm assuming this is because he wasn't notified I'm now following him and not because he just doesn't want to.
As far as the achievements app, it's cumbersome to navigate. It puts all the challenges first, which is somewhat annoying to me. It then lists achievements in huge boxes and you have to enter each one just to see what it was for. I thought going online and using the webpage instead would suffice, but it looks like Microsoft is forcing you to use the Smartglass app, which is designed the exact same way, except now when you go into a single achievement to look at it and then back out, it puts you back at the beginning of the horizontal page in front of all the challenges. Achievements are so hard to look through now that I don't really care. When you have a game like KI that has 94 of them, screw it. I don't want to spend 10 minutes trying to figure out what I do and don't have yet.