I'd LOVE to see a persistent thin client. One that you don't have to restart each time the network connection disappear for a second (it happens a lot with wireless connections) or when the system goes to sleep. It could be when you reboot the Xlobby server as well. It would be nice if the client could find its way again when the server comes back online without having to restart it constantly.
My wife gets enraged each time she has to click on that icon to perform any function that was there just a few minutes ago...
Same would apply to Pocket PC client and fat client.