A few days ago I started using Wave for some real projects. I found out that Wave is not really hard to use. The problem is that the network effect is kicking in, but in the opposite way.
Wave is a communication tool. You can use it to send messages and collaborate on projects with other people. And I think the problem here, is that the other people are missing.
I remember the first few years that I had internet. Not many friends were using email. I had email, but I had no one to send emails to. The same is happening with Wave now to. What use is it to send an email to someone, if you can't be sure that that person will read it.
I have a simple solution to this problem: install a Wave notifier. At the moment I use a notifier that works as extension in Chrome. It's non intrusive and shows a little number when I have new unread Waves. No interruption and I can take a look at the Wave that people sent me.
Wave me at email@example.com.