The Omni is a great hotel if you're in San Diego for business. I was there for pleasure, but I believe that the hotel is geared more toward the business traveler than the tourist. It is across the street from the Convention Center, and only steps away from the restaurants in the Gaslamp District. The hotel was very clean and modern, but in a rather bland way. It was comfortable enough, but not so comfortable that I wanted to stay much longer. it doesn't have a "wow" factor, and that's ok, as long as you know that ahead of time.
That said, my room on the 14th floor had a lovely view of the Coronado bridge and the Bay. The bed was not as comfortable as I've had in other hotels, but it was serviceable. The bathroom had shutters that opened to the room, which doesn't afford a lot of privacy (even when closed), so be aware if that bothers you. I didn't mind. The bathroom was exceptionally clean (a big plus!), but the shower pressure left something to be desired. My only complaint with the condition of the hotel is that the carpets in the hallway were a bit worn and lumpy. The hallway carpets made me concerned that my room wasn't going to be in good shape, but my fears were unwarranted.
The front desk staff were all very friendly and professional.
If you don't need to valet, save yourself some money and self-park in the garage across the street. The price (which may fluctuate depending on whether there is a baseball game at Petco Park), was at least $10 cheaper per night than the valet. Also, sign up for the Omni loyalty program ahead of time, to save the $9.99/day internet fee.
There are a lot of hotels in the same area from which to choose. I would return to the Omni only if I had a great deal, or if I was in San Diego for business.