I bought the individual issues. Does the TPB offer anything else apart from the inevitable foreword? I might pick it up if there's additional artwork or something fun like that.
There's no extras other than the forward.
However, they did do a lot of touching up on the colors and art--the "S" on some pages of the first issue is fixed to look better, the second issue has a lot of background color changes, Lana Lang's hair in the Smallville sequence is red-orange, etc etc. But I don't think there's HUGE differences.