You can read about 'em for days over at http://www.doublebasschat.com/forum/index.php
(well, after they deal with their little spammer/hacker situation they seem to be having right now)...there's a seemingly endless thread about Lamberts there. I've ordered a couple of sets from them, one of their New Deluxe (with the huge wound E) and the Resolution D & G set. Having played guts a bit (some cheap ones I bought and some very expensive ones a teacher of mine was using) I have to say that the Lamberts are pretty darn close, especially for something constructed from trimmer cord! My problem with them was the same as my problem with guts, though...not much definition at all in the E and A. But lots of people seem to contend with that just fine and love 'em. If you're looking for a string to do Rockabilly slap style exclusively this would be the string! Excellent click, and the low tension is fantastic for that style. Right now I'm using the Resolution set with an Innovation Rockabilly E and A on my Rootsrock bass, and that's a nice combo...good balance in tension and tone, very gutlike slap and plenty of definition in the lower end. They actually bow pretty well too!
Ordering from them is kinda skeery, true...you just send off your paypal dollars to their email addy (firstname.lastname@example.org I think) with a note of what you want and wait...but they do send you the strings. Keep in mind that it's just a one-man operation and Ivan doesn't really like dealing with emails that much, and that your order might take a couple of weeks at least. I had a little longer wait for the Resolution set, and had to send off a few emails to get a responce, but it turned out they'd been held up in French customs for a while, and Ivan had actually sent them off within the week I ordered them.