My favorite way to sync contacts is through Google. Just synch wirelessly to my gmail account and then magically every contact updates instantly on the phone and the PC, no matter where/when I edit it.

Note: To get everything to sync the way I wanted it to, I had to tell the phone that my Gmail account was an "Exchange" account, with the server m.google.com. I use that to synch my email and contacts. I went to a lot of trouble finding out that that was the best way to do it. Saying "gmail" type account wasn't satisfactory to me for some reason. I don't remember clearly now, but I think there was some kind of limitation of how the contacts synched that made the Exchange type account more palatable over the Gmail type account.

(For Calendar, I use separate a "Gmail" type account to synch the google calendar to my phone, and that works well).