I will not go into too much detail so I do not spoil the show for those who have not seen it, but it is a fairly standard sitcom that mostly has story-of-the-week episodes, with some longer story arcs that play out throughout the show's run. The humor is very raunchy. I am still amazed that they got away with some of the jokes they did. They also show off Behrs in skimpy outfits and Denning's cleavage in pretty much every episode. So, if sex and drug jokes offend you, definitely stay away from this show.
The complete series set is just the individual season sets packaged into one box. Similar to what was released for shows like The Office, Parks and Recreation, and the like. Hence, all the DVD extras are identical to those in the individual season releases. There are no extras that are exclusive to this set. Overall, the show was funny (if you like the kind of humor), well-written, and well-acted. The only thing I did not like about the series was the finale. I think it mostly felt like just another episode (with one exception) and did not give all the characters a great sendoff as series finales should. Overall, however, it is a very enjoyable show and worth checking out if you are a fine of sitcoms.