I love Prison Break. I bought season 1 and was TiVo'ing season 2. When I finished season 1, my TiVo deleted the first few episodes (keeping a max of 5 episodes). I was bummed, but I have the DVD to look forward to.
I'm also going to get the Heroes DVD. I TiVo'ed the show, but never got a chance to watch it before it started deleting.
The fact most shows come out on DVD is great. My friend was able to watch the first few seasons of Lost and now he's all caught up.