I happen to have a couple of iPods around the house and as a result a couple of extra dock connector cables. Until last night I was under the impression that they were identical to the iPad dock connector. They're not.
The iPod dock connector has "buttons" on each side that should be pressed when disconnecting from a charger. The iPad does not. As a result you may find it virtually impossible to remove a iPod dock connector from the iPad without the help of pliers. (Don't ask me how I discovered this.)
The two connectors look almost identical to one another so be careful. And if you find you've inserted the wrong cable, don't worry. It works without a problem. Just be sure to remove it from the iPad by pressing the little buttons on the side.