Previous Android user. Complaints since moving over.
Windows Phone Complaints
1) Live tile counter doesn't work most of the time for HeyTell, Facebook, GChat
2) Skype doesn't work in background mode. Android does. Makes app useless.
3) Messaging doesn't retain unsent text when switching to other app, home screen. Android does.
4) Can't view facebook like I can on my computer. Android does.
5) Reversing white background/black text for "night mode" like Nokia Maps does would be very nice in dark lighting, movie theather, etc.
6) Requires Zune to copy files off, unless emailed. Android solution is better, acts like a hard drive on USB
7) Auto-copy feature of pics to SkyDrive copies a small version of the picture, not the original size
8) Games that are for free on Android/iTunes cost money! Like Angry Birds.
9) Live Toggle Tiles like Connection Tiles don't update their wording when toggling
10) Market may have 10s of thousands of apps but a high number of them are just "hot girl" apps, missing many apps still!
11) Swype option is not available. Slydr option is a joke!
12) Volume hard buttons and Camera button don't always work when screen is off
13) Built-In "Listen for Music" option does not save what I find for music. Might as well just keep using Shazam/Soundhound
14) Scan barcode options should work like Google Goggles too.
15) Nokia Maps doesn't work in offline mode. Map doesn't load.