They even let you decide how often you want to get emailed. I chose once/day, but you could go all the way up to one email for every blip updated/added.
And this way works with all email, not just gmail!
There's a link in that email to send you straight to what's updated. How much integration do you want, exactly?
Really, all of Wave can be summarized by the fact that, at its launch, Wave deliberately refused to participate in any existing communications medium other than Wave. This meant that everyone you cared about had to get on Wave. Since that couldn't possibly happen, Wave was doomed from the start. Nothing about today's announcement is remotely a surprise to me.
Hard to edit your preferences, hard to get other people into it, hard to get reminders set up. If they could relaunch and make all those things better, Wave would be stellar. I almost wish they'd break backwards compatibility for people who loved the interface because it just went in the wrong direction.
The technology might be great but the launch and execution were really, really weird.
Well, they did originally have "who's online" functionality, but they had to yank it when someone found an exploit, and it took them forever to get it working again.
The "email me" option was much later - around the time they went from "Preview" to "Beta", I think. And as thorax said in his reply to me, Google flubbed the UI/usability of the preferences.
As far as "who has a Wave account", it's the same scheme as email. You get a Wave address; you're responsible for letting all your friends know what your address is (e.g., mine's in my HN profile). Probably could've been improved by hooking into Facebook/Twitter/etc. and spamming out your Wave address to all your friends...