Yes, I have read it, and I find it quite interesting -- not as a witness to any "historical Judas" but as a witness to the development of Sethian gnosticism in the second century AD. You may find second-century gnostic works quite esoteric and difficult to understand, as they have their own jargon and conceptual structure (dependent on Platonism, wisdom theology, biblical exegesis, and vestiges of Egyptian and Semitic mythologies), but they really do flow from the same proto-gnostic stream of much of what was accepted in orthodox Christianity -- one may compare material in the Gospel of John, Colossians, and Ephesians (e.g. the prologue in John 1:1-18 reflects a strikingly similar construction and interpretation of Genesis as the Trimorphic Protennoia). The Gospel of Thomas is probably the closest thing to the proto-gnostic stuff in the NT, and there is probably early and valuable material in the Apocryphon of James and the Dialogue of the Savior. And even second-century orthodox apologists drew on similar Platonic and exegetical traditions to develop their own theologies. I view early Christianity as a diverse mixture of different perspectives, drawing on different forms of Judaism and Hellenistic influences, which later differentiated in the second century to more distinct branches that developed in their own directions. This is an important point to understanding why gospels and tractates reflecting more mature gnosticism (i.e. those written in the second and third centuries, such as the Gospel of Judas) are not in the NT and why they never would have been contenders for the canon. Some had limited circulation only in certain communities; others were rejected in orthodox churches as heterodox, just as gnostics rejected certain "proto-orthodox" writings like the Pastorals. It is similar to the situation in the rabbinical Jewish canon -- the books that were regarded as authorities by the post-Pharisee rabbis did not necessarily include books (such as Jubilees, 1 Enoch, the Testament of Levi) that were authoritative for the Essenes, and even less the sectarian works of the Qumran covenanters (such as the Community Rule, the Damascus Document, the Temple Scroll). Canonicity was determined gradually by concensus and different communities made different decisions on what they regarded as authoritative. There is not one single Bible canon; we have a multiplicity of canons (such as the canon of the Catholic church, the Greek Orthodox canon, the Ethiopian Orthodox canon, the Nestorian canon, the Armenian canon, the Russian Orthodox canon, the standard Protestant canon, the Anglican canon, etc.). As for the gospels, there developed an early concensus (by the middle of the second century AD) in some early orthodox communities that only four gospels were recognized as authoritative. This is evident especially in the gospel harmonies of Justin Martyr and Tatian. But other communities had other views. The Marcionite churches accepted only one gospel, a version of the gospel of Luke. Other gnostic churches accepted a wider range of gospels and Jewish-Christian communities had their own gospels as well.
BTW, April DeConick has a new book out on the Gospel of Judas that challenges National Geographic's translation and interpretation of this text. She maintains (alongside a growing number of scholars) that Judas is indeed viewed negatively in this work.
