We have just gone through this gospel in a graduate Coptic class, in which we have also consulted some of the scholarly literature that has been generated since National Geographic published its rather rushed initial translation in 2006. To say the least, the translation and interpretation of this work are very far from settled. The trend in the scholarly world is to look with considerable skepticism on the notion popularized by National Geographic, namely, that Judas is portrayed as good.
In order to arrive at an informed judgment about this work, one must understand both the Coptic language and a lot about Sethian Gnosticism. One must study the usage of many words, both Coptic and Greek, in other related Coptic texts. (Coptic liberally borrows Greek words, and often uses them in ways somewhat tangential to their usual Classical and even Koine uses.)
This so-called critical edition includes translations in both English and French. There are quite a few differences between the two, some of them quite significant. Rodolphe Kasser, the author of the French translation, has a number of translations that are closer to interpretations suggested by scholars in the two years since the initial publication of the English translation. He also includes many informative notes that are lacking in English. The English translation is but little changed from the original, and it thus retains some decidedly infelicitious renderings. However, any reader who wishes to be more fully informed must consult the scholarly literature. General readers, as well as scholars, can benefit from books such as April DeConick's The Thirteenth Apostle: What the Gospel of Judas Really Says. It offers a very different perspective on the interpretation of the text, and also makes some important points about mistranslations in the original published version.
In spite of the cautions I am voicing here, if you are seriously interested in the Gospel of Judas, this "critical edition" is essential. It has photographs of the manuscript pages as will as transcriptions and translations. It is not the last word on the subject, but it is an indispensable part of the ongoing debate.