megan is pretty good. not only that but it serves it's purpose. seeing that since you have an es350, you aint gonna race it or track it like the is/gs guys, so you shouldnt have any problems with the megans. depending on the height you go for, be prepared to have a ride quality so distant from the comfort of the ES.
mine handles like a wooden cart or a go-kart. every single bump i can feel, my car's wheels go up from the ground when at an angle, it is bumpy on bumpy roads, smooth on smooth roads, but your es will look sweet

i'd say go for it. ive been wanting to see an ES lowered for the longest time (es350 mind you)