Its not often that I really like a mobile device. They have either compromised too hard on making it a phone while other models steer right away from that in becoming a PDA. The last one I actually used a lot was the imate SP5 which was a Windows Mobile 5 device. Windows Mobile certainly improved security with an inbuilt policy layer designed to enforce standards like passwords and delivered push email which is something Blackberry has had for ages.
One thing Windows Mobile 5 didn't have was the ability to set policy on the storage card. Now you can mandate the use of encryption on the storage card so that if it should fall into the wrong hands - you can wipe the device which wipes the encryption key and thus renders the card useless.
I like the fact that HTML email is now supported - rather than converting to plain text and then screwing up all the formatting on replies.
Some people have commented that the buttons are quite small. I'm not tiny and I've found that the buttons are fine. Other things I've noticed are that its quite quick to use and the inbuilt 2 MP camera is actually quite good. The only downside is the scrolling pad on the right hand side is a little sensitive....
The thing that really sells it for me is the 3.5G HSDPA support. Telstra has now released their HSDPA network which means a theoretical limit of 14.4MB though currently enabled for 3.6 MB!! They claim that they intend to make some improvements in 2007 to raise it to its full limit. That means I can use it as a modem with my laptop in areas where I cant access a free WiFi hotspot or ADSL connection. Add to that a 2GB Micro SD storage card and you can effectively download ISO images from the web straight onto your C730....sounds great to me!