Here's a short list of things I didn't like about my previous phone. In no particular order.
Screen is way too dim
You can insert emoticons into SMS and MMS messages, but the selection frame is just a simple rectangle - almost impossible to see depending on color scheme or light conditions (sun etc..)
the set became very loose after less than a year of usage
the built-in camera's produces grainy pictures of pretty bad quality no matter what
keys are hard to press, and sometimes you have to push pretty hard for the unit to repond to your actions
vibration is pretty weak
email alarms are limited to built-in alarms, most of them are not easy to notice in some noisy conditions (and you can't set the duration of alarm when incoming mail arrives!)
you can't enter more than one email address for a contact (are we in 80's or what? people have at least 2 accounts nowadays - mobile and computer emails)
power cord connector got pretty loose and easily detaches from contacts
the build itself is pretty cheap.. and the build quality as well as user interface quality is below normal level imo.
Well.. there's more but I'm tired :)