No, the Apple Pencil was designed to work with only the iPad Pro. The Pencil does not even work with other Apple devices such as the iPad Air 2, iPad mini models or iPhone models. If you're looking for a stylus that works with any iPad model, we suggest Pencil by FiftyThree. This stylus and all its features supports the third-generation iPad and later and iPhone 4s and later.
No, the Apple Pencil is designed to work with the iPad Pro and does not work with any other iPad devices including the iPad Air 2 or iPad mini 4. Perhaps future iPad Air and mini models will work with the stylus, but for now it is strictly an iPad Pro accessory.
The Apple Pencil is available for $99 from apple.com, Apple retail locations and authorized Apple resellers.
The Apple Pencil tip will "wear down over time," according to an Apple rep (via ars technica). Apple does include an "undisclosed number" of replacement tips with the Pencil, but it is unknown how much money additional replacement tips will cost. It is also unknown how quickly the tips wear out.
It is hard to believe Apple would release the $100 Apple Pencil without palm rejection, which is now a standard for any high end stylus, but there was no mention of the feature during the September 9th keynote. There is also no mention of palm rejection on the Apple Pencil page on apple.com, and images show users being careful not to touch the iPad Pro display with their hand while using the stylus.
Even though the Apple Pencil was designed to be an iPad Pro accessory it does not come bundled with the 12.9-inch tablet. Apple Pencil is sold separately for $99. Apple promises that its high end stylus is "highly responsive" with "virtually no lag." It also features pressure sensors that can detect a range of forces for drawing thin to thick lines, and it can "calculate the exact orientation and angle of your hand" for creating shading effects. The Apple Pencil can also be used simultaneously with your finger for blurring and smudging.