Students first... Forouzan is about as easy to read as any book on the subject. Since Forouzan has done a pretty good job of keeping the text up-to-date, however, you may find it difficult to use a previous edition of the text. I would estimate that about 20% of the material is either new or revised in the 3rd edition. The website also has some pretty good student resources, such as notes and related study tools.

For professors... I have been using the text since its first edition and have no regrets. In the third edition, Forouzan departs from the 7-layered OSI model to something he calls the 5-layered Internet model (Application, Transport, Network, DL, Physical), which may not be "standard", but it certainly makes things a little easier when talking about the Internet and modern computer networks. There seems to be enough quantitative material to satisfy those who wish to take a more engineering-centered approach to data comm, although I'm not sure how this text would fly in a school of engineering (my home is a school of business). There are ample online resources for professors, including powerpoint shows and exam materials. The only other text I would consider as a substitute for Forouzan is the slightly more technical text by Stallings, but as I said, I have never had any regrets about Forouzan.

I highly recommended this book for everyone interested in Computer Network, especially a student.