I'm not particularly familiar with IPFS: does it have some solution for free-riding?
BitTorrent as many have noted is great for popular things, even not-particularly-popular things, but absent incentives to continue seeding (i.e. private trackers' ratio requirements) even once-popular things easily become inaccessible as the majority of peers don't seed for long, or at all.
I guess what I don't quite is what IPFS adds vs. say, a trackerless BitTorrent magnet link that uses DHT? Or is it really just a slight iteration/improvement on that system?