I have purchased Nokia Lumia 800 and following is my feedback on the good and not so good feel on the device:
Not so good:
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1) After answering a call and when clicking on the "End call" button, the call gets cut but the "Ending call" message is shown on the screen and I am not able to navigate to any other menu or option(the phone hangs). Finally I have to do a hard reset(hold on the power button for a few seconds for the phone to restart). This happens at least 3 to 4 times in a day for me(on an average of 10 calls per day). The basic purpose of a phone is calling and this one, doesn’t serve the purpose here. So its really annoying at times.
2) Ringer volume not much audible in noisy environments. The Speakers could have been better.
3) The battery used to last only for half a day(a software issue which was later replaced by a new phone from Nokia). Now the battery life is one day.
4) Downloading of apps/games from Marketplace is not possible some time. It says "Your windows live id is unavailable at the moment. Please try after sometime" and this is annoying.
5) Live Notifications (Facebook, Twitter) don’t work at times.
6) No Equalizer in Music player / Radio and hence the audio output is good and not the best. Even the earphones provided along with the phone is no good in quality of audio ouput
7) Bluetooth limited only for headset pairing
The GOOD ones:
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1) User Interface is Excellent, equivalent to the iOS UI. No lags experienced.
2) The boot time is very fast(less than 10 sec)
3) Build quality is very good
4) Voice Call quality is good
5) Messaging is fun and cool
6) Email is awesome
7) Sync to PC is easy
8) Reliable and secure compared to Android
As of now these are the good/not so good things I have on my nokia lumia 800.