It will rev a lot easier, more so in the lower gears, the only thing you have to watch is the fact you will have less inertia, so on a hill for example it will slow down quicker as you start up the hill, but not even worth worrying about, had lightened ones on all my cars and always better than std, did have one done a bit too light and with hairy cams it was a pain in the arse around town, but running 300 degree cams, on 48's, so to be expected, and still on shitty clockwork ignition!!
I would get your spare sorted, as the lightening will unbalance it anyway, and have to be rebalanced.
tabetha