I'll try to write something that hasn't been covered by the other reviews. My background before reading (and studying) this book. JLPT ~3, and I knew ~400 kanjis (through the old fashioned memorization).
The Remembering the Kanji is *exactly* what it promises. After reading many reviews and forums, many people think it is something more. It is not.
What does it promise then? Luckily this time (unlike with many other books) you don't have to buy it blindly. Heisig has released a good number of pages freely available on his site, so you can decide before buying. Also as with any method, you have to review the the kanjis systematically. There is a website called Reviewing the Kanji, which although fan made, is done with quality of a commercial site.
One thing though that surprised me, not in a good way. There are stories only for the first 500 or so kanjis. After that, you have to be a little bit creative. But thats where the Reviewing the Kanji -website comes into help (see for yourself).
As you may have already read from other reviews, after reading this, you cannot say that you have mastered the kanjis, this is only the start. At most 1/4 of the work. Maybe even less. But it is quite possible to be able to finish the book in 2-4 months with the reviewing, depending on the time you use daily. After that, and with a basic knowledge of the Japanese grammar and words, you are able to guess new words very easily (although you don't know how to pronounce those). And when you see compounds, I have found that it is easier to remember those now if I know the individual kanjis.
As also pointed out by the other reviewers, the 2000 "general use" kanjis include some kanjis, that I cannot imagine being used daily. These include names of plants and some medical body parts. For those who don't think they are up to learning 2000 kanjis, there is a reduced list of kanjis called RTK Lite (Remembering the Kanji Lite). Check that out if you are interested.
This is not a book for everyone, but read the freely available pages, and if you are still willing to continue, I doubt that you will think that you have wasted your time.