I am teaching just 2nd grade this year and have finally realized my dream of having 1:1 iPads. That was made possible in part by Elliot Soloway of the University of Michigan donating some iPads to my classroom.--thank you!
While students still complete many paired and small group activities I love the fact that they each have their own device. It has allowed me to switch about 80% of math assignments to the iPad using a combination of TenMarks, Front Row, Mathmateer, and Splash Math. We are still using a text book that is not aligned to the Common Core, and while I do have students complete some of these pages (and other paper tasks such as MARS and Problem of the Month), it is fantastic to have Common Core aligned lessons readily available for math. I can easily differentiate assignments for students and small groups, they can get hints and videos as necessary, and I can spend more time conversing with students and less time shuffling/grading papers.
Another factor of 1:1 that students really like is the fact that they don't have a set amount of time to complete activities. Last year when my class was 2:1 each student might have 30 or 40 minutes to complete an activity, such as create a Popplet. Then they needed to hand the device over to their partner. After all, I had to keep that the iPad time "fair". Now students can go back to activities until they feel they're done. They also have the freedom to access apps as necessary without having to wait for their turn.