I've said this for a long time and I told them it when I interviewed with them. Tight integration between WP7 (or WP8) and the Windows desktop platform is their killer feature. iCloud is weak in my opinion and Google has no desktop OS presence to tie into and as much as I might want it to, Chrome and "the web" don't allow for (as someone else termed it) a well functioning and syncing "fat cache".

If I can make a Metro app for Windows 8 and hit all desktop and Win8-tablet users and get WP8 users for free or very little cost... I see the number of applications for Windows Phone increasing very quickly compared to their slow start thus far.