Stax, which recently launched in private beta, is a cloud hosting/deployment/ops platform based on Java appservers. The coolest thing about Stax is that it offers many flavors of JavaEE-deployable applications, including Python apps (via Jython) and Rails (via JRuby) with ready-to-roll built-in templates.
Stax has a very AppEngine-y feel, not just on the website, but in terms of the SDK interactions, local development, etc.
This is good news for all of the popular platforms ... and bad news for those rattling around the corners with non-standard APIs. As the app-hosting industry continues to mature, the emphasis will clearly be on established players like Rails, ASP.Net, JavaEE, Pylons, et al. at the expense of guys like AppJet.
It is true that some of these built-for-the-cloud platforms were designed from the start to default to hash-style or big-table style storage -- popular for content-oriented cloud apps because of its easy horizontal scaling -- where the "traditional" platforms focus on relational stores and have a variety of bolt-on APIs for cloud DBs.
But now that there are so many standard alternatives, it is unlikely developers will pay any custom-platform-tax no matter how elegant that platform might be.