Microsoft published an update on the Windows Live Hotmail roll out, "we're right on track with our release plan, having now upgraded nearly 50 million accounts on several different clusters. In addition to reason explained in earlier post about why it takes time to do the rollout, there's another reason;
"In order to turn on new features – features like conversation threads, QuickViews, and Filters – we need to build new indexes in the storage system for your email. These new indexes allow Hotmail to instantly show you mail from your contacts, or show you messages that contain photos, or let you organize your email by conversation.
We're currently running software on the site to create right indexes for all mail in your Inbox. That software must read from and write to hard drives where Hotmail data is stored. And, of course, it can't get in the way of you accessing your inbox or receiving new emails. When the indexing process is complete, we'll be turning on new Hotmail for all our users," explained Microsoft.