All depends on which app you will be using. I like paper by 53 and purchased their stylus.
Just had a look on their site, that's quite a nice stylus, does it only work as it says it does with the app or can it be used with other third party apps?
it will work with other apps too but only those who have used the API. I think at the bottom of this page, it states which other apps have integrated with Pencil. http://www.fiftythree.com/pencil I really like it and used it for a while. With apps that are not supported, it will work but not as efficiently.
I am like @highdefjunkie , sold my air and now have a pro instead.