A few months ago, I got myself a new PDA\Camera\Phone. It ran Pocket PC 2004 upon which I duly installed the .NET Compact Framework and sure enough, things ran.
ActiveSync was OK even if it wasn't as configurable as I'd like and it was fun to run Digger and Tetris with a stylus. The integrated camera was great - it produced pictures better than my first digital camera and with 128MB available, stored more than the original did. The video camera, MP3 player and audio recorder were great bonuses too. But its primary purpose is a phone and in that respect, it was shocking. Even at max volume, you couldn't hear it ringing. In a pocket, you couldn't feel it vibrate. It tended to lose signal in the middle of a conversation.
My XDA is now back in its box for sale on eBay and my 5 year old Nokia 6210 is back in service once again - it doesn't take photos but it is a damn good phone. Interestingly, the XDA hasn't depreciated at all. It's still worth six times more than the phone I've used to replace it. I think in this case, convenience and power is much less preferable to the specialized piece of equipment. It’s a bit like a proper stereo in that respect; only more portable.