Their app store, period.

I remember it during the 8.1 period, all you would find is slow garbage. I can't remember using a single app from their store that wasn't a slow mess. I'm betting it is still the case with their app store too. It wouldn't surprise me that the same issues would hit the windows phone app store.

Really? I had a windows phone from WP7 up to one of the last released and one of the reasons was that most apps were fast, snappy and started pretty quickly, while android phones in the same price range (about 50$) seemed to struggle with basic stuff.

Of course there were exceptions, but IMO that wasn't the major problem.

I remember all the scam apps. I would search for “Facebook” and there would be at least 5 apps with that name, all with the Facebook logo. The real one was somewhere in the middle of the search results, not at the top.