If you have a Windows Smartphone with GPRS (I'm waiting for the Symbian version) and an account like T-Mobiles unlimited $20/mth GPRS connection and love Skype then you will want to try out this beta. I'm sure this is the application I saw running on Niklas's iMate in Toronto. It's slick, it doesn't provide voice over GPRS, merely presence and text messaging. As a user of Agile messenger that's a pretty good start. Here's the link to the Skype Forum post.

We have early version of Skype for Smartphone available. Please provide feedback directly to me or in this forum.

Skype for Smartphone BETA
* participate in Skype network - log in, presence
* instant messaging
* centrally stored contact list support

Things to be aware of
* no voice (yet)
* network traffic usage - depending on your buddy list network usage can be quite large - up to several megabytes per day even without actively chatting, this is important if you pay per megabyte. There is option automatically disconnect then Skype is in idle and it's switched on by default, feel free to switch it off if you have flat-free rate.
Skype Forum