I use an earthway seeder for some crops like arugula, mini kale, carrots and radishes. I mostly do no-dig and am a big fan of the stuff that Charles is doing, but my methods may be slightly different. I broad fork once in the spring (it works well with my soil), add compost and rake smooth with a 30″ landscape rake. My compost/peat is fine enough to us the seeder in.
Overall the seeders are great for small seeds, but I like Charles approach for lettuce mix. I find a carpet of lettuce planted with a seeder a good cut at first but the next cuts are not great and the product suffers.