It used to say 75Hz on the Dell site but I think they changed it because people were complaining because it didnt work on all graphics cards. They had also bundled them all with only a single link DVI cable that only allowed 73Hz :doh .
The panel itself is capable of 76Hz without dropping any frames. It also beats most TN panels on Input lag tests as shown in this interesting thread.
http://hardforum.com/showthread.php?p=1034028590.
There is a monitor called the E2209WA which uses a TN panel and seems to be indentical to the P2210 except it has no displayport. If you can find them at your dell store it might be cheaper to get two of them with your P2210 and they all look the same. Neither of these monitors can do 75Hz though so you will be stuck at 60hz.