I tried to sync my Hotmail (Windows Live) contacts but every time I try it it freezes my phone, and I have to soft reset it, so I gave up, but Outlook works with no problem of course when syncing with my PC, I guess the advantage is that in case you had to hard reset the phone your contacts is backed up already on your PC, I use also Yahoo Go 2.0 and it also syncs contacts with your Yahoo account, there is also
www.Plaxo.com that will let you sync MSN, Yahoo, Google and even Outlook contacts and even calendar.