But this morning I was at a cafe, and wanted to see how it would work on a mobile browser--the iPhone.
When you pull up the URL, Wave sends you a message noting that your browser sucks. But they also give you the option to go on in. That's nice. 
Once inside, if you have any new pings, they come up immediately. I was surprised by how well this worked. It also occurred to me that a Wave app would be really useful to take advantage of the iPhone's push notifications--so I could get pings without launching the site.
Once you're in, you only see your inbox--although you can switch to a Contacts view as well. The Waves themselves look much like a messageboard.
When I went back into a Wave for the first time since last night, it provided me with a nice little activity summary right up top.
One neat feature in Google Wave lets you watch what others are typing, live. You can see their text as they input it. On the iPhone, you can stil see someone's input on the other end (albeit very slowly), but they, apparently, cannot see yours.
In short, Wave is surprisingly usable on mobile browsers--well, at least the iPhone, I'd love to see an Android collection where it would presumably work even better. (You'd hope.) As I test it more, I'll continue posting screen shots to this photoset on Flickr.
Oh, and for comparison's sake, here are some shots of the Wave dashboard in Firefox:
