I also have both the '11 13" MBA and the ipad2
2 completely different animals.
I use the ipad for catching up on twitter, books, magazines, news, web sites and some games and a bit of email, video, VOD... the mba is for core stuff like work, email, design.
Basically the MBA is my office machine docked to a monitor and the ipad is for as soon as i close the mba lid