Adobe Sketch allows you to draw and bring your creative community together in one place. Capture your ideas as sketches and share them on Behance for instant feedback. According to Adobe “Sketch gives you the freedom to find inspiration, explore ideas, and get feedback from trusted peers—wherever you are.”
You can buy up to 20 GB of creative cloud storage for $1.99. You get 2 GB free.
Adobe describes the app as follows:
INSPIRATION AT YOUR FINGERTIPS
Discover new art and be inspired by other artists on Behance when you launch Sketch. Combine research for inspiration and sketching for exploring ideas in a new, connected way.
SKETCH WITHOUT LIMITS
Sketch as much as you want; your ideas are never limited by the number of sketches you can create. Organize your ideas as projects in Sketch with simple touch gestures.
JUST THE RIGHT TOOLS
Sketch with tools that behave like the real thing. Create with essential drawing tools that interact naturally with the canvas: a graphite pencil, an ink pen, two blending markers, (brush tip, chisel tip), and an eraser. Draw with your finger or a stylus; the natural drawing tools respond beautifully.
GET FEEDBACK
Post a Work in Progress on Behance and get immediate feedback on your ideas directly in Sketch. Share updates as new revisions. And you can share with friends on Facebook and Twitter, too.
TOUCH SLIDE
Touch Slide is the most elegant precision drawing interface to come to mobile apps.
Draw perfect straight lines, circles, rectangles or triangles with this built-in digital ruler. Easily align shapes using on-screen smart guides and snapping.
CREATIVE CLOUD CONNECTED
Simplify the process of getting sketches off your iPad and into your desktop apps with the ability to Send to Photoshop or Illustrator. At the tap of a button your sketch is saved to Creative Cloud and sent to Photoshop or Illustrator where it will be open and waiting for you when you get back to your desk. Connecting Sketch to your Creative Cloud account also means your projects are automatically backed up, you can import your reference images and color your designs with your favorite Kuler themes.
BETTER WITH ADOBE INK
Designed to integrate beautifully with Adobe Ink and Adonit Jot Touch Pixelpoint™ pens. Maximize your drawing space in full screen by using the Pen Tip menu to change tools, colors and share your work—all with the tap of the pen.
iPad Notebook 
I don’t think the ADONIT PEN is that good. I tried it and is noisy and not as accurate….WORST part is go try returning it…WOW….you have to send it to TAIWAN, and you pay for it….then the company argues with you!!!
NOT READY FOR PRIME TIME…..cheaper and similar alternatives out there.