"Is it worth it" is always a very subjective question. As crowe put it, I've found it best for racing/flight sims. Then again, it's just the 3 monitors that cost, it's keeping enough power to play the newest games at an insane resolution (5760*1200 requires a LOT of horsepower).
I would suggest watching a lot of videos online and seeing your impression on the way it looks for you. Personally, I think the bezels are really the biggest weak side to multi-monitor gaming.
Hey, i just started playing mount and blade warband with eyefinity, and it is just so awesome to see those wide views of a cavalry line charging the enemy. So, totally worth it.
Also, although 3x 5:4 monitors has it's issues (with widescreen cutscenes being rendered poorly), I still think it's the best bang for buck (moneywise) that you can find. an entire 3 screen setup for 300 bucks (avg 100 bucks per monitor).
I toyed with the idea of getting another two monitors for some time. I definitely have the GPU power for it. It was going to cost me about $550 for two more Samsung 2494SW monitors and the displayport adapter. Finally decided against it because I don't actually game all that much these days, and I have other expenses anyway. I'm quite happy with my single 1080p 24", but at the same time, if I had the cash I'd go for it (although to be honest, I'd kind of rather get 3 thin bezel square monitors for the extra vertical)