I do a lot of event photography here in Denver; pretty much anything from conventions, conferences and lectures, to music and concerts, and everything in between. I know some people have been un-thrilled with the detail the 7D2 gives them in their bird/wildlife photography, but oddly enough, I think the 7D2 is a perfect companion to a 5D3 for events.
The ISOs and the extra reach (especially when you're forced to shoot from the back of a room), are incredible. I essentially got double the megapixels from the 7D2 (compared to the 5D3).
Here's a quick review and image comparo of an event I photographed last week.https://www.youtube.com/watch?v=3J3pS1-9fn8
PS: For those wondering why I picked 100mm as my point of comparison... I would've much preferred to compare 200mm between the 5D3 and 7D2, I just don't have two 70-200 lenses! Also, the room just wasn't big enough to justify 200mm on the 7D2, but hopefully, you get the point about cropping (images) vs. reach.