Have been using Magic Lantern for some time on 5D2. Was kinda hoping Canon would implement more of its features into 5D3. Sigh. Oh well, hopefully the folks at ML will be kind enough to provide some upgrades for us. Have really gotten lots of use of the time lapse feature amongst others. The video capabilities added are awesome too, though I seldom shoot video. not sure how I could force people to sit through even a short clip without having to worry about forcible confinement charges....

Don't think you need to fret about having space in your bag for the 70-200. Expect it will spend more time on the camera body hanging on the strap.