Software, software and software.
Crashes repeatedly requiring battery removal, a wait and a longer wait while it boots up again.
Keyboard lock doesn't.
Loses blue-tooth earpiece repeatedly and then gives up, requiring you to switch off blue-tooth and then on again, when it sometimes crashes as above.
When it works (sometimes for a whole day) it's great.
This is the second one I've had. The first was replaced after three repairs and software upgrades, and the new one is even worse in that it has added new crash tricks.
Battery life is excellent, even with blue-tooth active, and gives me (a heavy phone user) almost always a whole day.
Interior screen is excellent, although the image viewer is poor, handling only very small image files and failing to optimise them for the screen.
The exterior screen is far too vulnerable to scratching, and the keyboard lock's ineffectiveness means your phone regularly makes calls all on its own.
As a follow-up, below is part of a letter to Nokia accompanying the phone on its return to them
If 3) fails, as it often does, you must Remove battery, Wait for a couple of minutes, Re-insert battery, Wait for PDA to boot, Switch On phone, Enter password, Wait for it to complete, and then, roughly half the time, (within the PDA) access Tools, Enter, Down, Right, Right, Control Panel, a LONG wait while it sets this up, Select Connections, Select Bluetooth, Select Off, Wait, Select ON to re-establish Bluetooth earpiece connection, wait for confirmation, Select Done, Select Exit, Select Exit. If all of this fails, as the phone sometimes reports “Code accepted” but will not function and stays frozen at this point, you do it all over again.
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