I made this for dinner, and it was really good. I will definitely make again, as we eat a lot of homemade soup. But I changed or would change the following:
1. Left out the parsley because I didn't have any. It was fine without it.
2. Added a teaspoon of liquid smoke (of course!!) because everything is better with liquid smoke.
3. I didn't use the full 2 t salt. I used a few grinds on the onions plus 1 t, figuring I could add more at the end if necessary. It wasn't, and I always want more salt.
4. Next time I would wait to add the sweet potatoes and tomatoes until the lentils are completely cooked, then puree it. THEN add the tomatoes and sweet potatoes. (That would probably add 20 minutes to the cook time.) It would make it thicker and creamier, and you wouldn't get all the yucky watery chunks of celery and onion but you would get their flavor.
5. Next time I would use either a huge sweet potato or 2 medium ones. I just used one regular sized one because that is all I had, but if I were buying the stuff for it, I would get 2.
With those changes, I would give it 5 stars.
If you like thick soup, you could use 2 cups of lentils instead of 1 1/2. Two cups is close to a 16oz bag...maybe a little under.