I am in general impressed with Time Machine and happy with its unobtrusive nature and the quality of the backups. I’ve even been (eventually) impressed with how the UI works with Mail, although vast quantities of patience were required for the retrieval.
The irony of your Backup System Causing Your File System to Freeze!
I have experienced a lot of scary hangs over the last few weeks and it seemed that Time Machine being in a preparing backup mode was a likely trigger. This morning, downloading a VMWare Update, I stumbled across the VMWare 1.1.1 notes identifying the likely cause as a workaround for Apple bug 5679432 (Mac OS X hang under heavy disk load when unbuffered I/O is in use). So, not only is the original bug a deep OSX bug, it’s triggered by my regularly scheduled backup via Time Machine!