Since I use Google Apps for the @kugelfish.com domain, I tried out the new service by adding it to my domain from the link at this page. As for all virtualized apps, the administrator needs to create a new CNAME in the domains DNS records under which the new service will be mapped - e.g. reviews.kugelfish.com.
While there are many good arguments for an organization to use a hosted solution like Google Apps for providing their public email service, I am a bit more skeptical about outsourcing critical development infrastructure. Specially as in this case the SLA explicitly says that there is no SLA, since these are experimental labs applications - a step down even from the usual Google Beta label. But for organizations where code reviews are not yet a fully integrated and critical part of their development workflow, this is an intriguingly quick way to get started and hopefully become hooked on the practice of code reviews.