My opinion is that if you have to go to Letsrun to figure out how to used blood lactate levels to guide your training, then you probably shouldn't be using blood lactate levels to guide your training.
If you're an elite, you have a coach or sports physiologist doing this for you, and it might help. But if you're just winging it, with a blood machine and lets run threads, it's more likely to mess you up, than help.