If Microsoft wants to play seriously in mobile they need to stick to their roots. By that I mean leverage their superior position in the PC space down through tablets and then into phones. If they can make it so people want to port Windows applications to the tablet space and use them there, they'll come out pretty good.
While this sounds good in powerpoint, it doesn't work out so well in practice...especially when they had a beloved platform in WinMo and dumped it for Windows Phone.
And what about leveraging their superior position in the console market? Why not try to move into gaming tablets, then gaming phones?
beloved? A number of people I knew, including myself, were going for the Windows mobile 5 and 6 phones in that 2005-2007 period (those years may be slightly askew, but generally before everyone had an iPhone or Android device). The device specs were good, the phones had all the features, I bought Missing Sync to make it work well with my Mac; It all should've been smooth sailing.
But it just didn't work well. Email would quite often need to be reconfigured, it was awful at renegotiating connections and hopping from tower to tower, that one update (from Samsung or MS) that wouldn't turn off GPS correctly when you left the application that was using it, killing your battery in a few hours.. The list droned on.
Taken on their own it wasn't the end of the world but put together it felt like that frankenstein PC you have running in the basement that you didn't have a power switch lying around for and turn on by touching a screwdriver to the motherboard.
Maybe it was ahead of its time, maybe the OEM's just weren't paying enough attention, maybe Microsoft was trying to hard by including a start button and awful stylus. All I know is that damn near everyone I encountered with one of those phones was seeing people with Blackberries working as advertised and becoming very jealous. Add iPhone/Android in a few years and MS couldn't just leave it out there. They'd have been better off completely killing mobile than leaving Windows Mobile to compete with operating systems meant to be used on phones