Norton Critical Editions are often hit or miss affairs, but in this instance their execution was perfect. I shan't comment on the novel--if you're even considering it, you know it's a classic and on the short list of great American--not to mention, modern--novels ever written. What this edition does is make explicit why: it contains a series of Faulkner's commentaries on the novel from a lecture series at the University of Virginia; some excellent essays on the work by the likes of Stephen M. Ross, Cleanth Brooks, and a phenomenal formalist criticism by Eric Sundquist; as well as copious goodies interspersed, like a commentary on Faulkner's writing method and a few reprints of the novel's original drafts, both typed and handwritten. With a well written intro by Michael Gorra and a $7 (!) price tag, this is the copy to get if you're considering a little trip with the Bundrens.
EDIT: In the seven days since I posted this, Amazon has raised the price to ~14, which makes it somewhat less of a steal. I'd still recommend it, however, to anyone interested in this work as well as a thorough guide to its various nuances.