The Lean Cuisines I have looked at have an average of sodium in the 600-700mg range, and the American Heart Association recommends 1500mg as optimum (which is far lower than most Americans eat).
I have been watching my sodium, mostly because I used to salt the heck out of everything I ate, and my BP was affected negatively. Now I still have a couple Lean Cuisines a week, and I still do just fine with my target. I just try to make my "side dishes" (as one does NOT do the trick for me) low or no sodium, and keep an eye on the other meals in my day. One restaurant meal has probably 5 times the amount of sodium as a Lean Cuisine, so I just try to watch it. I don't think it's a big deal.
EDIT: BTW, I lost a good 70 lbs of the weight I have lost while still eating FAR more sodium than the recommended (like maybe 2-3 times as much).