The current Windows Mobile UI definitely has a shoehorned feel to it. Here are some of my complaints (these apply to the stock WM UI. I understand a number of more recent phones are putting custom UIs on top of WM, but I believe these are only skin deep and eventually you get to deal with the standard UI):
- It was designed for use with a stylus. I've become pretty good at using it with my finger, but it's not easy. It was originally designed for the slightly larger display of a dedicated PDA, but on my phone (an AT&T 8525) it's much smaller. You can adjust the text size but it only affects a small number of elements in the UI and would probably break the layout of the others if it were supported.
- The multitasking model is the most shoehorned aspect of WM. Imagine if you had Windows but could only run apps maximized and there were no app buttons between your start menu and tray icons/clock. That's what using WM is like. If you need to switch back to another already running app you go back to the start menu and "launch" it again. The OS is supposed to manage whether background apps should be told to shrink their resource usage or save state and shutdown automatically so the user doesn't have to care whether they need to exit apps or not, but this rarely works in practice. My phone came with an app (enabled by default) that always exits an app when it is closed. The phone works much smoother because of this.
I think the iPhone's approach is the better one. Only run one app at a time and always save state when exiting. You still have to go back to the home screen to launch another app but at least that screen has a nice big icons to touch and a nice big physical button to get to it (my phone has a little start menu button on it too but its actually easier to get to it on screen).
Also, the "window" management in WM is wonky. I once wrote a database lookup app for my phone. It had a lookup form and a modal details form. I found that if you switched another running app then switced back, it would bring the parent form to the front even if the modal child form was active, rendering the app frozen.
Again, the iPhone's approach avoids these problems by only allowing one app at a time. And even then, the iPhone apps I've used often use a navigational model rather than trying to fake it with full screen modal forms. I think the Android UI uses a similar model and I think it is the best for this form factor.
And IE moblie sucks. The fact that the next version of IE mobile is IE6 based is even more pathetic.
Anyways, the reason I didn't get an iPhone in the first place was that it didn't have 3G, ActiveSync with Exchange Server, and it used iTunes. Two of those issues have been resolved. And since I have a Zune, I don't really need to use iTunes much with an iPhone (just for updates really) so I wouldn't grumble as much about having it installed (as long as I don't need to leave some chunk of it running in the background). And it syncs with Vista's Mail, Calendar and Contacts apps too if I ever need that.