Edit: I confused Tixati and Fopnu, another p2p tool by the same dev when I made this comment.
Hmm. Reading the support page, it looks like there is no actual integration with i2p in the Tixati client itself. It looks more like an existing i2p client can function as a proxy, allowing Tixati clients to communicate over i2p. Similar to how a socks proxy allows Tixati to function over any remote network, like say a vpn.
Not un-useful, but the number of Tixati users is already limited on the open internet (and heavily slanted towards certain unsavoury interests). Finding other Tixati users on i2p just limits your potential peer group further. Mixing open internet connectivity with i2p connectivity also seems like a de-anonymization vector waiting to strike.
i2p would certainly benefit from a well designed easy to understand file sharing tool like Tixati. Specifically its focus on keeping libraries of files shared for longer periods, rather than the short-term burstiness of torrents, would be a good fit. But I would want it to be significantly locked down to the i2p network, and get some code reviews, before trusting it.