Want to download all sessions of #MSIgnite 2015 easily? Simply use this PowerShell script fresh from the community in the current version
Channel9 Session Downloader v1.81
adapted by Michel de Rooij which is available in TechNet Gallery.
This version even opens an UI where you can select what to download:
All events and sessions are available in different formats via a RSS-feed, like http://s.ch9.ms/Events/Ignite/2015/RSS/mp4high. The PS script utilizes these data feeds and transfers the files to the specified path on your computer. The download works with BITS.
There's also an older but functional script at Ignite15Videoandslides.zip (and many more versions) available.
Enjoy the (downloaded) sessions!