My fiancee and I just finished a 4 day cruise to Catalina Island and Ensenada on Carnival Inspiration. The ship is looking great after its refurb in 2007, and we both commented on how it was far superior to the other fantasy class vessel we took out of New Orleans two years ago.
We had a nice window cabin on the upper deck amidships. No great shakes. The view was unobstructed, and the cabin was in good shape. I have never had a better shower--the water comes out at 5,000 PSI and it can be anywhere from 32F to 195F. Ok that's exaggerating, but I like my showers lobster boil temperature with as much pressure as possible, and Inspiration delivers.
Catalina Island was good fun--we took a semi-submersable tour and saw the giant kelp forests and a huge amount of sea life. Very nice. Had a MASSIVELY overpriced lunch at a trendy cafe. Also nice.
Ensenada is a hole; a dirty tourist trap. We took a horseback riding excursion through Carnival, as I wanted to spend as little time in town as possible. Got some great pictures from a ridge above town, overlooking the pacific. Then we spent a little time in town haggling with street vendors over wares created by China for American's Visiting Mexico (TM)
Back to the ship--we enjoyed all of the dining venues. and found the quality of the the food to have substantially improved over our last Carnival cruise. There is no added-fee restaurants aboard, which I prefer as it puts a bit more pressure on the MDR to produce quality goods.
We didn't see any of the shows (heard rumors they were great) or spend time in the casino. The Adults-only deck aft was nice, but only had one HOT tub (there was another tub, which was, for some reason, tepid). The waterworks area was great fun.
Overall, if you want a nice, quick, inexpensive cruise, this is your best bet.