I used windows for my Phone to take backup and
update contacts. (This will be one of two
reasons to use, other is Phone Software Update).
Today I found a application on linux. It was quite cool.
Command Line based "GAMMU".
it worked better than my expections, Even
my Nokia 5800 is not working other than "Info"
mode, but N82 is fine.
Gammu has a Phone Database.
I put my entry here and
filled a bug here
Starting response is good and hope to fix in coming version.
Yes, it has GUI ("Wammu"),
Contact Editor and Other Screenshot
It has Windows GUI also (not used yet).
Hope it will fix soon and able to work with Nokia 5800.