I don't like the frosted glass look...it's obviously an attempt to tie in with iOS 7's frosted glass effects.
But that's not my main problem with it. The middle-grey tones of the Mavericks dock makes quickly finding apps much harder. Not enough contrast for icons that are not very dark or very light in tone. Also too much visual noise -- the same reason I keep my menubars opaque instead of transparent.
So, taste and aesthetic aside, using the Mavericks side dock increases cognitive load, and thus makes me less productive while working.