Check out this video review on ShowMe App on the iPad Lessons YouTube channel. The video is more than a simple review. It's also a brief tutorial, and helpful for understanding its advantages and also its limitations.
Browse (for free) tutorials made by members of the ShowMe community. English, Social Studies, Science, Language, Math, and General are the current categories listed. Click "Common Core Lessons on ShowMe" at the bottom of the page for a list of lessons aligned with Common Core.
A California sixth-grade teacher shares how she has used ShowMe in her classroom. She uses them for students who miss class, or need to review a topic covered in class. She likes the fact that students can stop the videos at any time, to "control the pace of instruction."
A Technology Integration Specialist explains how she's introduced iPads to the elementary classroom. They've been used for previewing texts, studying vocabulary, giving differentiated spelling tests, and supplying background knowledge for students to prepare them for tasks/assignments. She includes a list of useful links to examples of teachers using iPads with their students.
In this video from ShowMe, a middle school Principal and a Speech Therapist share how ShowMe has helped their students demonstrate knowledge and teachers share their lessons. Yes, this is an ad for ShowMe, but you might be inspired by one of these ideas.
The biggest drawback, for me, with writing on the iPad is the fact that you can't rest your hand on the screen. It's very different from drawing, and difficult to do for beginners. This easy trick (cutting the thumb and first two fingers out of a cheap cotton glove) does the trick without paying for an expensive, specialized stylus or tablet glove. Watch the video for a demonstration. I tried it, and it worked beautifully, for the price of $1.99!