I use 3 23 inch monitors and don't think I could go back to even using 2 honestly. Gmail and google voice live on my left, photoshop/illustrator live on my middle on, and quickbooks and excel live on the right. I have all my photoshop and illustrator workspace windows on the edges of the side monitors so when Im working on art i have the full monitor to view the art at the largest size i can.
Buy ones with the narrowest bezels I could find and the best color you can afford. Like Pierre said, IPS is the best panel for accurate color, and you should honestly look into getting something to calibrate the color across the three monitors as well.