The app choice may have been woeful 6 months ago but is now rather good. Instagram and Vine being the two major omissions and they are now confirmed and due for release shortly.
I have far more apps installed on my Lumia than I ever had on my Android phone.
Sky Go is very likely soon too.
Many of the major games publishers are pledging to release WP versions at the same time as Android and iOS.
Bear in mind in Europe at least WP market share is around 11% and Apple just under 15% and in places like India and South America WP is more popular than iOS so app manufactures are having to take notice.
I am running the Release 3 version of WP (official beta tester) and its rather good and once Nokia Black is released it will move WP to an even more potent competitor to the big two.
If you’re going on contract and cost is not too much of an issue you can’t go wrong with the Lumia 925 at around £27 p/m
If you’re going sim free then the 620 or 625 is where my money would be.
EDIT – note it is not worth comparing the Nokia 800 / 900 to the new WP8 phones. WP7 was released too early and was by no means complete. The experience on the new phones is far superior. Yes I did have a Nokia 800 also!