There are many mapping apps out there. This latest OS bit of kit looks to be a very cool thing. I love the OS.
For me the best map thingy EVER has been Bing's unique take on mapping. Used to be Microsft's "Live" Maps and changed its name half a dozen years ago to Bing. It hosts a great aerial satellite view with a drop down on the right side of the screen. The dropdown options offer aerial and Ordnance Survey mapping (plus others). It also offers a neat 3D (Bird's Eye") view which can be rotated by 90 degrees at a time by clicking the rotate arrows when in Birds Eye mode.