I use the wifi and Cisco VPN client to connect to our corporate network. I then configured email to use imap and I can get email out of our Groupwise system. So, for me anyway, it is a valuable tool. As long as you have access to a wireless access point, you get great web surfing (Safari, although I wish it supported Flash Player 🙁 ), better than average email, google maps, youtube, weather, stocks and now with the 2.0 upgrade lot's of apps that 3rd party developers have written. Oh yeah, it plays music and videos too.
Does it have all of the bells and whistles that the iPhone has? No. But it is close.