Whether or not you need third party software can depend on your own use patterns. Many routers now have good setup and configuration options. With my original version WRT54GS version 1 (they I think have got up to version 7 or greater now), I was having issues with torrent connections. DD-WRT firmware allowed me to change some extra tweaks that overcame that. Others find that third party firmware can increase power settings (but that would increase the wireless radiation
), and other wierd and wonderful stuff. As said you only need third party firmware if you come accross a particular issue.