Never been ringside at a fight, but I don't think I'd like it at all. The angle is all wrong. You're below the action, and most likely will miss most of the action on the other side of the ring. I agree that seat capacity is the biggest factor. I've seen fights in 10-12 thousand seat colisseums, and there's not a bad seat in the house, no matter how cheap the seats are. I've also been in an 18 thousand seat colisseum and felt the upper seats were a bit too far off. I still enjoyed the hell out of the experience, though. By far the worst venues for watching fights are those with a lot of flat seating area. You can be many rows back, and still be below the ring, an angle I positively don't like. These are venues not specifically designed for boxing, but used anyway.

Either way... nothing beats watching fights live, especially with a group of friends. Also, you'd be surprised at the number of hot women that like to attend live boxing matches.