I cannot remember how you do it (did it a month ago in the SDK) but you most certainly can pull in your contact lists. It pulls them into contacts and then you can merge them together to make a combined list of contacts with telephone number, address, e-mail, IM, etc.

So instead of having to remember what Dave was called on AIM, ICQ, Yahoo, MSN, Skype, etc you can merge all his details together into the Dave contact - so you know whenever he is on regardless of which IM he is using. Once you select Dave from the contacts list (who will show up as online if he is on any of the IM services assigned to that contact) it will show you specifically which IM he is currently on.

There is one drawback, I expect it will not auto-update (as you have to explicitly import it I think) your IM lists as there is no practical way to do that for a combined list, but it shouldn't be too hard to remember to update if you add anyone new. Personally I know I will find the benefit of merging all a persons different IM names into a single contact FAR more useful than the minor drawback of having to add new contacts to the N900 manually if I add any new ones to the PC.

In fact, I doubt I will even use IM on the PC any more once my N900 arrives as it makes more sense to keep all real-time communication on the always-on portable device.