If all wireless devices attached are working properly then you can leave well alone.
http://www.linksys.com/international...fwid=30&coid=6
Is the UK firmware (this is different to the US as it has more wireless channels.
http://www.linksys.com/download/vert...4v4_ver_eu.txt
Yours is the first official release. If you need anything listed in the above document then you need to upgrade. The upgrades talk of fixing lockups and modified buffering for improved performance, so they may well be worthwhile.