I'm sure premium 4 letter net domains might have some worth, but the non-premium domains won't have anything at the moment, all LLLL.com's just got registered around October 07 therefore it'll be a while before LLLL.net's are worth something.
I just ran a scan of all premium LLLL.net's and have published the list. There are still over 15000 of them left but they will run out by the end of this year. I would suggest regging a few good ones and holding them for two-three years.