Received my 4i and 5i recently but haven't gotten them out on the course yet. I can say that they're a lot chunkier than I thought they would be. There's more club to stare at than the i5xx series in 4i and 5i.
I bought a 4 and 5 to play with my Blueprint S 6-P. Hard to get ahold of i230 individual irons in good shape, and even then they're within shouting distance in price to the new ones. Figured why not. Now I'm anxiously waiting.