Years ago I went to a party where the hosts were playing a U2 concert on their very large TV and it seemed incredibly strange to me to own a concert DVD. Does anyone seriously sit down, put the DVD in, and watch a concert for 2 hours? As it turns out, no. But they DO provide a really great way to have some awesome background noise and some pass-through entertainment while you're cleaning the house, hosting a get-together, etc. You should find some good ones and put them on your Christmas list.
We currently own only two (Allison Krauss & Union Station and John Legend), but we definitely need more.