For me the main things are
1) Calls / Texts
2) A proper PIM system
3) A phone that integrates seamlessly with my pc and whatever office software I choose. Activesync and Sync Centre can be complete nightmares. I often end up with 3 or more sets of data in outlook. Grrrrr.
4) Decent processor/ memory so the phone loads and runs apps quickly.
5) Ability to add memory cards
6) Big Touch screen, stylus
7) High speed net connection
8) Push email
9) Decent battery life, mine does spend a lot of time sync'd to my pc whether at home or work but when you have to travel decent battery life is really necessary.
10) Open OS
11) Unlocked or unlockable not that sony ericsson crap sorta unlock.
12) Not the size of a brick !!!!
What I would like
a) decent media player
b) customisability
c) a reset button back to factory settings to enable brick recovery would be nice. To reset phone/bios/OS entirely. Flashing bios scares the crap outta me.
d) min of 5 megapixel camera with flash
e) wifi/ bluetooth
f) GPS
g) slidey out keyboard thingy
think I may be waiting for a while
maybe I'm just too demanding