That completely turns off the transparency for everything. Isn't there a new option to have dark font colors for icons on the screen? That would be really useful on lighter wallpapers.
The new "Darken Colors" option only darkens menu button type elements, such as "back" or "calendar" "inbox" "today" in the calendar app, etc. Basically it makes very minor changes. The home screen still kinda sucks. I used to use dark wallpapers because I think they look slick. Now the dock turns to an extremely ugly black-ish-grey and I can't stand it. So I stick to one that makes the dock kinda blend with the background.
If you're trying to get the white title of apps underneath the icon's pop more, then I don't think there is anything you can change for that. Even changing the font size doesn't adjust the app title sizes.