Ok, I use Plaxo (no, it's not something you stuff chickens with! (does that 'port'**?))
However, Plaxo currently bugs me - perhaps terminally so.
For one thing (the main thing!), it knows that a lot of people in my address book have disappeared – it knows this because 'update' requests to them bounced.
Ok, so, what would you like to do with 'duff' contact info – bin it right?
However, Plaxo doesn't offer an option to delete these (now) useless contacts (duh, like how did they overlook that?)!
I can't see why their add-in can't easily do this – they've obviously got in the knickers of Outlook, and they know what bounced – so why the hell don't they offer this feature! I think Plaxo initiative/inventiveness is pretty damn good – and I just hope that the product gets better (real soon!)
**Paxo – a popular stuffing mix in the UK – and it's available worldwide too (God, I love the Interweb!)