I am having a strange issue with iTerm2, in terminal vim (non-gui) and the solarized color scheme. First, I have set iTerm2 to use the dark solarized colour scheme.
The above answers didn't work for me.
I'm using iTerm2 with vim 7.3 on OS X 10.7.4.
If the above solutions didn't work for you too, try this
syntax on set background=dark let g:solarized_termtrans = 1 colorscheme solarized
Update: According to Jim Stewart, this works on Kitty too.