lucy24 - 2:25 am on Mar 1, 2013 (gmt 0)
Mine says "MSIE [1-4]\." The quotation-marks-and-escaping combination is, uhm, belt and suspenders. Or belt and braces, depending on where you live. Will probably do no harm, but isn't needed. But if you do escape a literal space, you should escape literal periods as well.
The trailing period was, ahem, added after the release of MSIE 10. MSIE 5 exists in versions other than .0 but I've got some exemptions involving the extreme north of Canada, so 5 and 6 are handled in mod_rewrite.