I have used the DD-WRT firmware quite a lot over the last year or so and must admit it has many more featues than the Linksys standard firmware, but I have to say I have encountered problems with my wireless connection stability when using it.
I tend to try it when a new version is released but always end up back on stock firmware.
If you are intending to use it though, the lite version should more than suffice for the vast majority od users. If you don't like it then just go back to what you using previously.
This is a good place for you to start with that v5 mate.
http://www.dd-wrt.com/wiki/index.php...rsion_5_WRT54G