"Wave is currently a limited beta and invites are at a premium."
Not really anymore, I've got 11, my mate has about 17, google have been forking them out at quite a rate of late... Still it isn't like I can dish them out, it isn't in a state where it's any use to the normal person, I mean seriously in order to search public waves you need to append with:public to your search, making a wave public is an arse too as you need to add public to your contact book every damn time you log in. -.- honestly.
Some of the apps are neat like the video sharing app that you can synch time with other people active on the wave.
But less email, it really reminds me of an old threaded bbs with flashy media inserts.