The 30's are great if you can afford one of those. If you don't want to spend the money on a 30" and you play somewhere with resizable tables, then a 24" one works fine that has 1920x1200 resolution.
If you want one thats bigger than a 24 but still want to get out cheaper, HannsG has a nice 28" monitor that has gotten great reviews. Great for the price also, currently $599 w/free shipping at Costco. Think I am going to get one of those myself.
http://www.costco.com/Browse/Product.asp...&lang=en-US