originaly i lowered mine 40mm, didn't notice any wrong with the handling, it was just flatter going aroun dcorners, with alot less roll...
now im on d2 racing coilovers, and ive dropped it as low as it will physically go, (ie i cant get a piece of paper betweem my tyres and the arches :D)
handling was messed up majorly but once i got it set up it runs fine, handles like a dream, and sticks to the road like glue.... but i do get a huge amount of tyre wear on the inside, i changed my rears the other week, 1 side was bald on the indise and i still had 2mm of tread on the outside, this is mainly due to the set up, i asked for the 2 degree camber adjustment, better for corners bad for tyres lol