So the first stumbling block I've hit is to do with my use of Google accounts. My primary email, calendar and contacts are through a Google Apps account so I can have everything under my own domain name. Wave is not currently available under Google Apps so I have to use my normal Google account to access it. This means that my contacts are not available to me. I suppose I could export all contacts from Apps and import them into Gmail but they'd get out of sync quite quickly.
This is going to be a persistent problem with many of Google's services until they're all fully integrated and available using an Apps account. Picasa is another example which would benefit greatly from integration with Google Apps.