Anyone care to explain what, if anything, I'm missing?
Cisco and a whole bunch of others have been trying to put together a comprehensive suite of tools to do all this, but so far they've failed to make it feel seamless. Google might change that, they've certainly got the resources to make it happen.
Just like there was already free email before gmail and search before google came along, it's a major event.
But I agree with you that all the components have been seen before, maybe with the exception of a system like this having an API.
This is why gmail-to-gmail emails arrive so quickly.
More generally, rather than using point-to-point protocols to make N(N-1)/2 pairwise connections between N people, there are certain new possibilities if everyone just maintains a single link to a document (a Wave) hosted on the server.
Wave is kind of the inverse of P2P. Downloading is more efficient if you can simultaneously download from N people. Uploading is more efficient if you only need to upload to one server.
however I can imagine super productivity in communication/im for teams sitting across continents.
A tiny advantage of wave is that you can watch your colleague typing realtime. Those two minutes of impatient waiting (specially during a heated discussion) now would be drastically shortened. You could forget IM etiquettes during 'waving'.
I also thought of similarity with etherpad (specially the code while on the phone interview which was discussed earlier on HN)- where the interviewer may see the interviewee coding live.
imho, google wave may not matter now, when the users grow to decent numbers, we will find out.
PS: your gmail id becomes your google wave id (I had a good wave-id in the sandbox, i ended up getting my gmail account to the public preview).