While the main feature is mostly intact (the commentary from the regular version is not present), several special features had to be cut. The remaining features (all on disc two) are:
-"Don't Say You Love Me" music video
-"Ash's Journey" introduction video
-"The Story of Mewtwo's Origin" (short version)
Overall, I wouldn't say there's a particular reason to seek out this edition, unless you want to own a copy in every format the movie's been released in.