In short, this is an excellent book when used in the appropriate context. It is meant to be a textbook for advanced human anatomy classes that take a regional approach (i.e. med school gross anatomy); there is no better regional anatomy textbook.
This was the main text for my gross anatomy class, and the professor also recommended Netter's Clinical anatomy (which is rich in clinical content but not the best way to learn structures/landmarks). As a textbook Grays is very good; it has a great combination of descriptive and accurate text as well as fairly detailed pictures. Personally, I wish that it had more pictures with more labeling. The drawings are not as good as Netter's Atlas of Human Anatomy. Netter's Atlas, however, has no text, so I always use these two resources together.
Gray's Anatomy for Students was designed to be a textbook for REGIONAL ANATOMY classes. That is, students take a region (say Head & Neck) and learn all of the important bones, nerves, vessels, organs, and tissues in that region. A systems-based class, by contrast, teaches all of the important nerves in the body (across all regions), then moves on to all of the bones, then moves on to the circulatory system, etc. and not necessarily in that order. This is the best textbook if your goal is to truly master regional anatomy while taking a class. I am not sure it would be very useful for a systems-based curriculum so try to find out what your class involves before purchasing this book. Gray's also contains a fair amount of clinical content which is interesting, but may not actually be useful to you.
If you are considering Gray's for USMLE board review, it is much too dense and contains too much detailed information for that. For board review, get an atlas (I recommend Netter's) and a condensed text like BRS Gross Anatomy by Chung or High Yield Gross Anatomy. See if you can look through those texts to decide which format you like better. Even BRS contains way more info than you need for your boards, but is an excellent tool for mastering gross anatomy. I don't actually know much about the High Yield book. So, Gray's for Students is excellent for a regional anatomy class, not good for quick review. I should also mention that the student consult included with this book is great to be able to access the full text online from anywhere. It also allows you to download many of the images, which could be used for study and presentation.
If your goal is to teach yourself anatomy without taking a class, this book may be a good resource but is NOT the kind of book you read cover-to-cover. You will only be able to learn so much anatomy without taking a class (I tried before taking my class). Better and cheaper resources for self-teaching are the Netter Anatomy Flash Cards and the Kaplan Medical Flash Cards. The Netter cards are by region, and the Kaplan Medical cards are by system. They are both excellent.