I've only watched "Evolution" so far, and WOW did it look good. The colors are vibrant as hell and the bolder lighting style really pops off the screen (especially compared to how flat and lifeless everything looked in the second season).
The new, light gray carpeting on the bridge really jumped out at me as well. I never realized it was that bright before.
Unfortunately the episode itself is still a bit of a snoozer. Once you get past the amazing effects, it's basically another "stuff goes haywire on the Enterprise" story (which is a plot device they used way too often on this show), together with another tedious "Wesley learns a valuable lesson" story.
I love Evolution for many reasons...the character bits, both with the guest actor and Wesley. The treatment of both an alien species and an artificial intelligence (this episode gets 5 stars simply for there being no Kirk to talk the AI to death). The indroduction to the masses of nanotechnology. The use of baseball metaphors. The wonderful music and FX. There really is nowhere this episode goes wrong.