when i did my lessons it was on two line wipi free airs for the first two days then a mid aspect 4 line naish on the last day (cant remember the model)
we started unhooked on the free air. we were taught to launch unhooked, get in the water, hook in, put the board on your feet (keep an eye on the kite so it doesnt stray and pull you around), *then* unhook and go.
we did hooked in launches on the naish, and i was quite dissapointed at the time as I was used to the pull coming from much higher (ie, from my shoulders) so whenever I tried hooked in i was pulled straight over the board, sometimes getting air and face planting stylishly.
not that it really matters cause after couple of months or so you will be starting any which way you please