[they] will provide customers that are currently under maintenance for Zend Studio 5.5 a free upgrade to Zend Studio for Eclipse. If you wish to continue to use Zend Studio 5.5 simply renew as you would normally and licenses will be provided for both products. Any Zend Studio purchase will entitle customers to use both products.
I have to say that I am rather in the "I can achieve better results without Eclipse" camp, but will try the new version nevertheless. So far, the IDE looks very good. The only minur issue I found is that it ships with a quite old version of JRE (1.5.0_08_b03, which translates to 5.0 update 8; the latest version as of today is 5.0 update 15 or, even better, 6.0 update 5). Oh, and the PHP 4 version that comes with it is 4.4.7.
While downloading the Eclipse version, I also found out that "classic" Zend Studio 5.5.1 has been released about a month ago. New features include Leopard and Vista support (finally!); the versions of PHP and Zend Framework have been bumped to 5.2.5 and 1.0.3.
When using the "check for updates" feature of my 5.5.0a installation, it neither showed me the 5.0.0b update nor the 5.5.1 version. When installing 5.5.1, it refused to use my 5.5.0 license key, though. I contacted support and will update this entry when this has been resolved.
Update: The Zend support staff regenerated my license, Zend Studio 5.5.1 now works seamless. And make sure to read the comments: Obviously, the Zend Studio for Eclipse 6.0 release is from January — but it's still not clear why one local Zend subsidiary sent me an email on the "new" release yesterday
First time when I read this post, I went to Zend website and tried to download the 'latest' software, then I realized that I had already installed it many days ago because I had a local copy of Zend Studio for Eclipse 6.0.0 which was downloaded on 2008-01-22 10:44 PST.