With many of these products, the case held the new iPad just fine

Where it starts to get dicey is with form-fitting accessories that were designed to fit the iPad 2 precisely. We've tested dozens of form-fitting iPad 2 cases, keyboard cases, stands, and mounts today, and a few didn't accomodate the new iPad at all, while others worked but didn't fit quite right.We encountered frequent fit problems with folio-style cases. With many of these products, the case held the new iPad just fine, but the case's openings for accessing the iPad's controls, cameras, and ports didn't line up perfectly. And on a few others, the front cover wouldn't properly activate the iPad's magnetic sleep/wake feature. The reason here is that these cases require you to slide the iPad into the side of a leather, rubber, or fabric frame, and the new iPad's extra thickness often kept it from sliding all the way in.iPod Nano Accessory Review: iWatchz Timepiece Collection .The result is that the iPad didn't quite line up with cutouts for the camera, side switch, buttons, or ports, or the cover didn't close properly. If you've got an ill-fitting folio case, it will likely suffice until you can get one that fits better, but it's not a great option.
Similarly, most the book-binding-style cases we tested, such as those from Portenzo, Dodocase, and Pad & Quill, had fit problems. These cases are made with internal wood or plastic frames that grip the corners of the iPad with precision, and those corner grips just can't get all the way around the new, thicker iPad. If you're interested in this type of case, you'll want to wait for a version made specifically for the new iPad—all three companies, as well as a number of other vendors of this type of case, have announced such models. (One exception here was Xhibt's iPad 2 Flip Case, which fit fine.)
On the other hand, we expected to have problems with shells and skins, which tend to be form-fitting, but many of the ones we tested—especially those made of silicone or other materials that stretch a little—fit the new iPad well. For example, iLuv's Flex-Gel Case fit the iPad 2 like a glove, but it's just flexible enough that it also works with the new iPad, if a bit tighter. For some others, such as Speck's rigid Smart Shell for iPad 2, the case fit, but once it wrapped around all of the new iPad's edges, it was obvious the case was made for something slightly thinner—there were a few gaps between the iPad's body and the case where the case was being stretched a bit too much. In general, the shells that didn't fit tended to be those made of especially rigid material, those that barely extended around the sides of the iPad, and, of course, those that had little to no wiggle room with the iPad 2—these often couldn't firmly attach to the new iPad.