Quick update from the wallet upgrade: I've now a mostly finished version of I0coin implemented on top of the bleeding-edge Bitcoin code, see
https://github.com/domob1812/i0coin. The only thing still missing before we can make a release is a patch I submitted to upstream Bitcoin that is necessary to fix a defect with headers-first syncing. (The issue is present in Bitcoin as well but much more severe for short block times, long chains and merge-mining -- all combined by I0coin, unfortunately.) And, of course, some more testing.
If you are not afraid of compiling the code from the repository, you can even give it a try right now. If you want to do that, please use the "temporary" branch, i. e.,
https://github.com/domob1812/i0coin/tree/temporary. You may also need to -connect=51.254.131.226 (my own already updated node) for the initial sync. After you have all headers, you don't need this anymore and can connect to any other node as you like. Running (ideally publically reachable) nodes with this code helps strengthen the network for when everyone upgrades.
It may be possible to update without redownloading the chain (i. e., just leave your existing data directory), but I have not tested that. Be sure to make a backup of everything before you try, in every case! Also, please do not yet mine with the new client on a larger scale -- you can test mining a few blocks, but not too many consecutive blocks (you definitely shouldn't activate BIP32 or BIP66 on your node).