I am using this book in the course I am teaching at Villanova this semester. The first seven chapters cover the basics of software architecture in Dr. Gorton's concise style. A case study is used to illustrate concepts throughout those chapters. The latter chapters cover different hot topics in the software engineering field, like model-driven architecture, service-oriented architecture, etc., and were written by guest authors. I chose this book because of its recent publication date, its focus on middleware and the author's direct style.
Update - Feb. 2009 - What follows is an excerpt of my review of the book for my "course retrospective", which was written at the end of the semester: "If I were to teach this course again, I would investigate other textbook candidates. The textbook used this semester was Dr. Ian Gorton’s Essential Software Architecture. I had selected this book for several reasons: recent publication date (2006), coverage of current/emerging trends, business solutions focus, realistic case study, concise writing style and availability as an e-book from the library. This book was fine and met our needs, particularly when supplemented with current online articles. However, I found that perhaps it is too concise for students just learning the material. Therefore a more traditional textbook with helpful educational aspects like key words, review questions, homework assignments and a glossary would be more beneficial to students."
One other point I would make is that the latter chapters of the book exhibit a high amount of variability in terms of the quality and tone of the writing. This is due to each chapter being written by a different author, and therefore isn't unexpected -- yet I found it distracting. In particular, inconsistencies in the amount of factual information and the manner in which it was presented posed a challenge when using this book in a classroom setting. Overall, though, Dr. Gorton is clearly an expert in the field, and his experience pervades the sound design advice he dispenses throughout the first half of the text.