ViEmu/SQL in SSMS 2008 but I think it did the same thing in SSMS 2005.
The biggest problem is related to pasting. Even a single line of code can get messed up and it tries to auto-indent the pasted line.
But if you past 3 or more lines then one of three things happens: nothing abnormal; something throws an exception; the lines get reformatted with tabs inserted at apparently random places in the lines of code.
There are a couple other oddities which happen when updating code, such as the way single quotes disappear as you are editing a literal - its trying to help and it works well on straight insert but gets funny when you edit.
If you want I can get the details of the exception. I passed it on to the SqlPrompt folks but did not get details back.
I try to remember to turn SqlPrompt off when I paste a bunch of code; otherwise I save and close the buffer and start editing the file again and everyone is happy for awhile.
After the exception things work pretty normal except for a few ViEmu features - the main thing that does not work is undo.