Yeah. If you're going to go with a multi-screen setup, 3 screens makes sense with the shooters. You don't want the crosshairs split between monitors as in a dual setup.
Peripheral vision is definitely lacking in the shooters on the standard 1080p. 3 monitors would maximize this and make it more realistic in the left/right direction, but then you give up 500px in the up/down direction that you'd gain on the 2560x1600 30" monitor.
I think the 2560x1600 offers a good balance of additional up/down and left/right real-estate compared to the standard 1080p monitor. It doesn't offer as much on the periphery compared to the 5760x1080 3-monitor setup, but more and more games, especially shooters, require vision in a vertical direction as well.
Additionally, the 30" ips monitors, in general, give the best image quality, color, and viewing angles. The longer response time on these monitors is arguable as well as there is no standard companies use to measure monitor response time relative to other monitors.
Through this exercise, I feel like I'm talking myself into one of these things.