I just had Omaha Steak Burgers last night! The 6 oz ones, got those free a while back with some Top Sirlions I ordered. Omaha is great for convienence, everything is individually wrapped in vacuum pouch, but the quality is on par with most local butcher shops and Omaha is twice the price (usually when you add in shipping). I will say though, that thier Vintage Filet Mignon is really good, although the only way I've ever gotten those is when they've called me offering them.
So if you eat 1 or 2 burgers at a time this is a good deal (since you won't have to waste anything and it's easy to take 1 or 2 out), for a large BBQ just go to the butcher. I have never had the 4 oz burgers, but I assume that they are the same quality as the 6.