One of the things I believe that Google Wave should have is a sort of notification system that tells you when someone has added something to a wave. I get that Google Wave might eventually replace email, but for the meantime (until everyone gets their Wave account) my email inbox continues to be the page I always open up first.
So if you have Google Wave but hate to have to open two windows, one for gmail and one for wave, I got good news for you, there is an extension called Wave-XMPP that you can add to each wave you want to get notifications from.
To add this extension add the following address to your contacts firstname.lastname@example.org , now add this contact to any wave as if it were another person.
click the subscribe button.
Every time some one leaves a new message on the wave you’ll be notified via chat of this change.
I got the message twice because I edited something on the wave.