I've received an invite for Google Wave! And i find it incredibly interesting. There is so much potential for the Wave application to become my entire internet day-to-day experience. For example, i quickly whipped up 2 gadgets:
http://davidgoemans.com/gadgets/gmail.xml
http://davidgoemans.com/gadgets/twittergadget.xml
Which embed a GMail gadget and twitter gadget ( the same from iGoogle ) into a wave. This GMail gadget is more like a mobile GMail, which i also found the embed for from iGoogle's add stuff. Unfortunately, the default iGoogle GMail gadget can't be embedded in wave, and if you try and embed full gmail, it takes over the entire browser tab.
But those are just cheap 2 second gadgets anyone can make. Robots provided a lot of power too, giving me the ability to import my twitter timeline and keep it up to date. With a bit of work, the robot which i started: twee-bot@appspot.com could easily become a flexible social client which exists on a wave. Currently, however, the Wave API is not what it says it should be. And when Google fix this and allow, for example, things like the FORM_BUTTON_CLICKED event, i may actually be able to continue the work.
Feel free to pillage and plunder those gadgets and import the robot ( not that it works ). And expect a tutorial on how to make a working robot sometime.