This developer deserves our praise for being 1st to release a Mavericks-compatible Tweaker/Maintenance tool!
In 10.9 as well as prior OSX versions, 2D/3D Dock has only applied to Dock appearance when positioned at bottom of my display; dunno if this true for other users...(???)
However, the "2D" toggle in iTweaks 5 doesn't alter my Dock's 3D tray appearance even when positioned at the bottom. (It does quit/relaunch when I click "Apply".)
Anyhow, I'm contentedly "stuck" with a 2D Dock on my 27" display, because accessing the Dock from either side is easier/faster than keeping it at the bottom — which often requires me to lift & drop the mouse to get there.
So, I'm really hoping to find a way to restore Dock Transparency, which has been disabled by default in 10.9. That new, military gray background must satisfy the post-apocalyptic esthetic which seems to have overwhelmed Jony Ive recently. I could forgive his obsession, except the gray messes with legibility of fine details and the app status lights on my Dock Icons. I found a bucket-full of PNG resources inside the Doc.app, and I suspect that some combination of 'em is responsible for generating the Dock background. If that's true. then Dock transparency is probably beyond the scope of apps that "tweak" hidden settings, since some PNG resources might need altering (hacking) in order to restore Dock transparency.
I'm hoping some geek wot's smarter 'n' me spots my lament, and will offer some useful insights on how to restore Dock transparency... TIA!!!