I like to use GViM for editing files in Windows. Given that ISE supports using an external editor I immediately went about setting it to use my preferred editor. What I discovered with ISE 10.1 was that ISE keeps an open handle to the editor when editing files. This is stupid! The issue is very problematic because ISE has a tendency to crash, and with an open handle to the editor, it brings the editor down with it (at least with gvim.exe). ISE 11.1 was recently released and sadly it has the same issue. The CR (Change Request) I got filed with Xilinx to fix it will only be done with ISE 12.1. What I do for now is open gvim outside of ISE, and then double clicks in ISE will open in the same gvim that I'm using without having that handle connecting gvim's existence with that of ISE.
ISE crashes - gvim lives :)
This relates to my post about ISE stability issues.