Here are two problems I've found for specific shows
1. Pole to Pole
Search gives two results for this series. At the time of searching, one result took me to a page saying that Episodes 5, 7, and 8 were currently available. The other result took me to a page saying that only episode 6 was available. I don't know if the same happens on a V6 box, but this could be a problem of the 360 box interpreting iPlayer data differently (or incorrectly), or it could be an error in the way the information has been added to iPlayer. Either way, all episodes are available directly from the iPlayer web site.
Search gives two results. One for series two, available on demand, and currently being broadcast on BBC. The other is a link to the box set of series one, available for purchase from the Store. However, all episodes for Series 1 are available on iPlayer right now, so why does the search result not include this series?