I'm on MacOSX Mountain Lion, using std terminal. When I open two files in the 'working buffer' using :vsp the buffer allocates the two files correctly in the working buffer. However when I close one file the buffer switches to a 50-50 split instead of the initial. When I switch through project tree and code using 'ctrl+ww' it automatically re-adjusts the buffer in the initial (and optimal) size.
I report this to #vim / freenode and told me to report it here as a bug.
I'm using project v1.4.1, vim 7.3 compiled via macports