I'm getting close to the point where I'm going to return my Defy XT's. I am only using one of them currently and have asked my daughter to use the second, but have yet to receive feedback from her. My current complaints which seem to be very persistent:
1) Frequent warning messages to replace battery with an official Motorola battery (requires reboot)
2) Frequent warning messages that the SD card is defective/damaged (requires reboot)
3) Occasionally some unspecified process seems to be running in the background and makes the phone get super hot and drains the battery in less than an hour (yup, reboot). I have tried shutting down all background process except those necessary to actually get the phone to run when this happens and it does not help.
4) Even after a reboot I almost always need to again reboot the phone because of strange problems with the home screen or the above issues being unresolved by the prior reboot. Just this morning I had to restart the phone 4 times before it started behaving normally.
5) Pathetically weak/feeble GPS. The Optimus has far better GPS functionality.
6) Applications headaches: I cannot seem to add much in the way of applications because none of the pre-installed apps can be moved to the SD card and some of the apps I have installed (e.g. Spotify) seem to require installation to the phone, I am at a point where I have 48 mb of free memory and cannot install or update some apps due to memory restrictions (once again: Spotify). At least with the Optimus I could specify installation for most apps to the SD card but with the Defy it seems I must install to the phone first and manually move the app despite trying to select "install to SD" as an option, but for some reason it is hard coded to prevent this. If I could offload things like Facebook to the SD card this would free up a lot of space.
I have been using smartphones in various iterations for years and PDAs before that (original PalmPilot!). I have a long history with these sorts of devices and in my experience, the Defy XT is one of the most unstable and poorly functioning devices in the class that I have ever encountered. Despite its limitations, the Optimus was a far more stable and reliable device than the Defy XT.