I've made no secret of the fact that I am a fan of Plaxo. The ability to backup and replicate contacts and calendar information, combined with the ability to automatically update contacts with new information, make it a killer app. I've been using it for a long time.
- It synchronizes across many new data sources. As of Friday I had one master address book and calendar, in Plaxo, which now feeds Outlook (and by extension my Blackberry), hotmail, and GMail. While Plaxo can import LinkedIn contacts, it doesn't synch them back, which is too bad. Nonetheless, I've now combined all my address books, deduped them, and synched them back. That's a first.
- It now knows how to behave in an Exchange server environment. Previously, if you installed Plaxo on more than one PC attached to an exchange server, you would have bizarre behaviour including multiple items replicated in the address books and contacts. Now it knows about each and every PC, and ensures that updates happen correctly.
They've also become much more open, implementing SyncML, which means that any SyncML enabled address book or contact list should be easier to integrate with Plaxo. Nice move!
I haven't played with their slick new web UI much yet, primarily due to the same observations as Om Malik and Robert Scoble made — it's slow. Nor have I played with their new (and very nice looking) mobile app, since they only support US carriers.
Plaxo 3.0 is a great step forward.