Had an awesome time at the Padres game and loved my seats. Could see every part of the field just fine. Petco is a fairly big park but has a small feel to it, I would assume because they have so much outfield seating. Seats are comfortable; on par with what I've seen in other ballparks I've been to. The elbow and leg space was adequate but not too generous. I've seen much worse (Fenway Park, Dodger Stadium).
Stay away from the rows in the 20s, those are too high up and will take you out of the loop as far as what's going on down on the field.

I'm a San Diego native and have been to probably 24 MLB stadiums thus far, and Petco isn't in my top 10. But its not a bad stadium at all, just very plain to me and that could be because it's new. There's no history here yet and it's a shame you can't see the Coronado Bridge and surrounding water at Petco. Maybe the design wouldn't have fit facing that way and plus, if that were the case, the Western Metal building probably wouldn't be here. That thing looks cool here at Petco. They have an awesome selection of local beer though which is a big advantage.