^Tennant had already been on the podcast commentary for the episode. (Along with RTD and director Alice Troughton.)
I finished listening to the commentaries this afternoon. Although there is some variation in quality, they're all enjoyable listens, with only limited dead air. Personally I found the ones on "Silence in the Library," "Midnight," and the two final episodes most interesting and entertaining.
The deleted scenes are a bit on the dull side. Apart from the original framing sequence for "The Unicorn and the Wasp," they don't add much. More interesting is the chance they offer to see what footage looks like prior to filmizing and the addition of music and effects.
The featurette is firmly in the Confidential tradition of offering endless clips interspersed with inconsequential comments from the production team, but it's even worse than the typical episode in lack of interesting contact. If you want a gentle overview of the four series so far, this is a nice way to get it, but there's no real making-of content here.
Tennant's video diaries are probably the best extra; I wish he'd done more this year. The first is memorable mostly for Tennant and Gardner's incredulous enthusiasm for their police escort, while the second captures a variety of nice moments during the shooting of the finale, including a John Barrowman attack, a Lis Sladen interview, and Catherine Tate and Billie Piper discussing baked beans in hot chocolate. Not to be missed.