I'm pretty torn on the Google apps on Microsoft thing. On Wp7 Google was pretty clear that they weren't going to make apps for that system and that if Microsoft wanted their users to have access, they needed to upgrade their browser to the latest webkit technology and then they could use maps, gmail, youtube, etc. and get the same experience we get on desktop... which is pretty awesome. It's not as good as having a dedicated app because of notifications, etc... but at that point MS was just like, "oh they have Bing, no biggie, Bing is better!"
Now they're reaping the benefits of having a terrible browser that ignores the latest tech and telling the company that pretty much owns the internet to bugger off.... Could Google gain some awesome points by going in and helping them? Sure, but ... why? MS acts like a child and if I were Google, I wouldn't be too concerned about 1.5% of the market.
The biggest kicker? MS has already told it's customers that it's going to stop supporting WP8 in 2014. Why would Google develop an app for a platform that'll be replaced next year? That's terribad.