I2P version 0.7.5 foremost addresses network stability issues by adjusting how exploratory tunnels are built if a router nears its connection limit, and also by distinguishing between connected peers and other non-failing peers while picking them for inclusion in tunnels.
This version also delivers fixes to installer behaviour on Windows, to the Router Console, NTCP transport and UPnP mechanism.
Additionally, version 0.7.5 changes the "news.xml" file location where I2P routers check whether a new version is available. Instead of the old URL (http://complication.i2p/news.xml) a new location (http://echelon.i2p./news.xml) will be used. If your router uses default updater settings, it will start using the new URL automatically. If not, you will need to visit configupdate.jsp, and change it manually. For a while after this update, the old news.xml location will also redirect all HTTP requests to the new one.
Finally, since Complication is withdrawing from the I2P project, to make some far-reaching changes in his life, this update removes Complication's public key from the list of release signing keys. You should expect the next release to be signed by zzz instead. If you have non-default updater settings, you may want to remove Complication's public key manually, by visiting configupdate.jsp, and removing the key line starting with the characters "JHFA". If you wish to verify whether this information is correct, please check the GPG-signed release announcement.