I have a WM phone, a Verizon Pocket PC XV6700. It stinks. It has poor battery life; I got it specifically to run one particular application, which was developed as a WM-only application (against my advice...) and when that app is up, the _extended_ battery runs out in under six hours. This means that I have to keep charging the phone.
The OS itself will just plain die, without warning, and without notice. I'll be busy and notice that I've not had any calls for an hour or so... and try to call out. No connection. I turn off the phone, turn it back on... Connection. And three missed calls. And yet, according to the phone, I had a signal the entire time, three bars at least. What happened is that the OS just froze.
When I attempt to log in with the web browser, the OS will freeze at least 20% of the time. That's unacceptable. When it does connect, the displayed web pages load slowly and are often unreadable. I have stopped even trying to use it as a web device.
The phone hates to synch up, both on Macs and Windows systems. Because of MS's pettiness, Apple's iSync won't talk directly to Windows Media devices, so I had to buy a 3rd-party app (Mark/Space's Missing Sync for Windows Mobile) and I often have to disconnect and reconnect the phone two or three times before I get a proper connection so I can sync... and it's not Apple's or Mark/Space's fault, the same phone behaves similarly with the sync services built into Vista. (Don't know about XP, haven't tried to sync with a XP machine. I suspect that it doesn't work properly there, either.)
Note that I have another phone, a Motorola RAZR. In the same locations where the XV6700 gets three bars, it gets four. It never hangs or freezes. Not even once. It is recognised by iSync _and_ on Windows... and can sync using either Bluetooth or a USB cable. Including the very same USB cable that I use to attempt to synch the XV6700. And with the Motorola, I can connect first time, every time. Same cable. Same computers. It appears what where-ever the problem lies, it's not with either the cable or the software on the computers. I suspect that it's not with the XV6700 itself, either; as I'm not the only person who has to use that not-sufficiently-damned WM app, other people at the office have WM phones and all of them tell the same story: poor browsing capabilities, system hanging and freezing, poor syncing, poor battery life.
Thanks to our experiences over the last two years with WM, we have demanded that the WM app we need to use be re-written for iPhone or Android or something, anything, else. The developer didn't want to do it, but got on board after our CEO called his CEO and ripped into him with a point-by-point description of exactly why WM sucks and gave 'em the choice of doing the re-write or losing us as customers.
We will never, ever, buy anything which requires WM ever again. Period.