I have been using I2P for a while, and I think it's pretty good for what it is. Sharing files through bittorrent is great, and I have gotten very good speeds from it surprisingly enough, so that's a huge advantage over Tor which discourages torrenting. Address books are a neat idea and very easy to use, and even if the default lists you are subscribed to aren't that great, there are others which are more complete and up to date.
There is no Freenet-style decentralized distribution of files nor is there yet any functional integration with IPFS, so you are forced to get data from central servers and in case it's down you are out of luck, "try again later :^)".
It doesn't try to integrate with clear net, something that in my opinion is a good thing because as it's demonstrated by Tor, it brings too many problems. Although many of these come from the retarded and non-anonymity-friendly nature of HTML/CSS and JavaScript, so many of those problems are still present in I2P.
That's as far as I can say about I2P. Haven't really tried the others except for Tor, and only sparingly IPFS, Zeronet and Freenet.