Windows Phone is gaining a lot of traction in the enterprise market. I see a lot of people who have a windows phone as their work device. Its pretty common for me to see people with WP on my commute these days. In fact I would go as far as saying it's uncommon that I won't see at least 1 WP every day. A year ago it was a very rare sight.
the app gap is still present, but it's nowhere near as big as it used to be. Most companies now at least have wp in their thinking when making apps, even if they do come late and without the same quality as the iOS and android versions.
the biggest improvement has been the feature improvements over the last year. I mean when I bought a windows phone, there wasn't even rotation lock or separate volume controls, let alone a notification centre. 8.1 was a big step forward and made it a viable option for lots of people, and convergence with Windows in W10 will make it even better.
On marketing, I think they need to stop these "honestly" infomercials. Just have some cool music, with pretty people taking pretty photos and using some cool apps and stuff. There isn't enough time in a 30 second advert to give people information about the logical and productivity advantages of a product. You just need to put windows phone in peoples minds by having a huge volume of short and simple ads.