I recently switched to xterm-256color in my konsole, but I found that vim looks exceedingly ugly, unfortunately. The colors were all washed out and difficult to read with reduced brightness. I decided to explore some alternative color schemes, including popular ones like solarized etc., but they just don’t work for me – I have the default color scheme burned into my mind and I really like its high contrast even though I can easily stare at it for 12+ hours in a row. It also works great even in adverse light coditions on a notebook.
In the end, I didn’t find any dark vim color scheme that would just look like its default 16-color color scheme. (Light background color scheme looks mostly the same in 16 and 256 colors by default.) So I had to create my own – 256like16.vim, drop it in ~/.vim/colors. You may want to edit yours to add some more bolds to make it look exactly like the 16-color scheme, but I ended up liking this one more, after all.
(You will need to install colorsupport.vim so that GUI color settings are used in the 256-color terminal. This particular script worked by far the best for me, and :ColorSchemeBrowse is also great when exploring schemes.)