ShoreTel will often have a controlled release of software. For example, Version 9.0 might be shipping to new clients but will not be availalbe to existing installations until it is declared GA. Existing clients with a compelling need, could always obtain the upgrade, but it would be subjected to the terms of a controlled release. Over the years I have observed that an 8.0 release, for example, never goes GA, but becomes 8.1 when it does. With the release of Version 9, ShoreTel has now formalized this "enhanced delivery" process.
Starting with ShoreTel 9 add-on feature sets will be made available as "dot" releases in the form of 9.1, 9.2 etc. The impact of this new development process is taht features delivered in a "dot" release will not be included in the first major release of the next version. So if you are on 9.1 you will not be able to upgrade to a controlled release (CR) of 10.0 butt will have to wait until 10.0 goes GA with a 10.1 release.
So we witness a fomalization of a process that has really be in use for quite some time! It is a process, however, that has built in software assurance as the primary goal. If you have an interest in the latest feature set, send me an email and we will update you!