The windows team blog posted a message to all of the eager customers waiting for the new rollout of Windows Live Hotmail Wave 4. The update hasn't been going as quickly as most users would have expected, when it began rolling out two weeks ago.
The Hotmail team made a note that the rollout does not go by country, language or anything else, but updates by what cluster your account is located on. So users using multiple accounts may notice that one mailbox has been updated while the other hasn't.
The Hotmail team mentioned that they have ran into some minor problems with the update, adjusting a few things “under the hood” in the early stages of the release. The rollout has only been released to a single cluster, among hundreds of clusters, which covers a few million customers, less than 1% of all Hotmail users.
Amongst the hundreds of clusters is different hardware, as not every cluster is identical, which will require additional testing. During this week the Hotmail team will be testing the new version on these clusters to assure everything is running smoothly. Once testing has completed, the remaining 99% of the customers will begin seeing an updated mailbox, however, the team said this will still take a few weeks to finish.