I've had a Lumia 920 for about a year now and I'm kind of just tired of not being on the iOS/Android bandwagon. Since I've had the phone, WP hasn't had a meaningful/noticeable update and there are some pretty big flaws.

The biggest being no central notification center. If you receive a toast notification from more than 5 applications (you can pin 5 to your lock screen) you'll have to hunt for the 6th app's tile on your "home?" screen (the hot mess of tiles dumped onto your screen) just to see if you have a notification or not. Assuming you have 2 email accounts (1 work, 1 personal) and send text messages, this means that you really can only afford to put 2 other apps on your lock screen. Hilariously, if the application isn't on your home/tile screen, swiping over to the applications list won't help because the tiles there don't update or display toast notification count.

Another issue that I've noticed more recently (while trying out some of the mediocre applications in yawn-inducing app store) is that, because of the tile driven UI, I don't actually even know the names of some of my applications. The real issue is this: I can't have multiple pages of tiles like iOS & Android, so I have to throw them all onto one page that just turns into a wasteland of small tiles. If you use big ones, this wasteland will become so large that you'll find yourself forgetting about applications on the bottom so I try to keep it small. The other problem this causes though is that I'll "unpin" rarely used applications which sends them to the applications list... but because I'm used to seeing them as a tile, I don't even know THE NAME OF THE APPLICATION so I have to scroll around this application list looking at the tiles hoping that I spot this thing like some kind of police lineup. This sounds stupid, but it happens... I'm talking about rarely used applications.

I'm sure I could think of more. Most of these problems are just subtle annoyances... lots of little "workflow" issues that go unrecognized until you really start to use the phone a lot. Restricting tiles to 1 screen really sucks. I try to include only the apps that I use often on my home screen... but everything else... I'll never touch it again. Remove a tile from the home screen is a big deal. As soon as you demote something from the home screen, you'll probably never use it again. If I had the luxury of multiple pages of tiles, I know for a fact that I'd use more of these things, but once your tiles get 20 rows deep it just feels dirty, inefficient and unorganized. Some applications benefit greatly from having a large tile as well... weather apps and stock portfolio apps... so those alone can take up 2 entire rows.

Edit: Another issue that I thought of is that I was assigned some awful XBOX Live username "Player1045748#####" and I've tried to link up my actual XBOX Live account (which I don't ever use anyway), but I can't actually figure out how... so I've just given up. It's not a huge issue for me though, but might be for the gamer types. To WP's credit though, all of the games get lumped into a Games tile

Edit: Sorry, this is really poorly written, I'm not actually as illiterate as this reads.

/rant