We have sailed on Celebrity and Norwegian and they have been great or exceptional. I knew that a 4 day cruise to Catalina and Ensenada on the Inspiration was not likely to match those trips. I was right but give the cruise a "4" rather than "average" because it is a good value and as long as you aren't expecting too much, you won't be disappointed. This was over Thanksgiving and the ship was full - I suspect that isn't unusual and would have thought Carnival would have worked out some of the rough edges better.
My sister and nephew came along to get their first taste of what cruising is like - they thoroughly enjoyed the trip. We also had two 15 year olds with us who had a blast in and around the teen club. Food was very good - once you got it (see below).
Port of Long Beach, not LA. Right alongside the Queen Mary with a very convenient parking garage that seems to have enough spots to handle the two ships that Carnival alternates from the location.
Bed was roomy and comfortable. Lots of closet space. Nothing fancy but all bases covered. Attendant was great - staff throughout were friendly and helpful.