Pros:
* Works wirelessly - so if you're on your network your Mac just goes on its merry way backing itself up. Note Time Machine it does differential backups - so just backs up the changes every 20 mins or so
* Can connect your existing USB drives to an Airport extreme. This becomes a shared drive that you can then use for Time Machine on each of your Macs
* Can connect multiple USB drives to the Airport Extreme
* New Macs will backup using Wireless 802.11.n (draft) - basically it much faster than a traditional wireless 802.11.g network
* If backup hard drive crashes it can easily replaced

Cons:
* Wireless connection will be slower than a wired connection
* Was a bit tricky to setup (see below for some tips)
* If you deal with a lot of large files (eg Video) this may be too slow for your network
* Initial backup may be very slow - it's worth connecting via ethernet cable directly to your Airport Extreme
* Only works with Aiport Extrem or Time Capsule, so you need to think about replacing your exisiting router.

Going to try and keep this blog article up to date with info: [www.999reasons.com]