Using Vim/Gvim with multiple GUI windows

Currently gVim cannot have separate 'toplevel' windows for the same process/session. There is a TODO item to implement an inter-process communication system between multiple Vim instances to make it behave as though the separate processes are unified. (See :help todo and search for "top-level".)

Take a look at GNU screen used in conjunction with Vim.

First window, start up gnu screen and vim

screen -S edit

Second window, connect to screen session:

screen -x edit

Incredibly useful over large xinerama desktops, multiple virtual screens, or VNC sessions. One session of Vim, with lots of tabs, is all you need.

-- Tom

It's been some time since you asked your question and many things have improved. Nvidia has much better driver support for multiple monitors on Linux.
I've now stopped using Gvim since I moved over to KDE: Now I'm using vim-qt. It allows you to open multiple instances, in case you don't want to use vim in the terminal.

edit: My setup