We just returned (January 2009) from the Dominican Republic and used the Rough Guide as our principle source of information during our travel. I had hoped that the book would come out before we left. I had the earlier edition but knew some items were out of date. This edition arrived around Christmas and we left on Jan 12 for 10 days in the DR.
Read the first 55 pages of the book carefully. Unless you have a lot of time or are a very superficial traveler, you will not be able to see all there is to see as described in the Colour Section. However, the Basics section is accurate and very informative. Even then, there are some corrections. When we left, there was no departure fee (p51) but the sign indicating the fees was still up with the fees blanked out. The cost of a phone from Orange (p54) was around RD$600 not RD$2000. We bought one for our stay and then gave it to a work group from Canada when we left.
We drove throughout the eastern half of the DR so I can not speak to the accuracy for the rest of the country. However, for where we were, the book was quite accurate although a bit optimistic in spots. What no book can accurately convey is the friendliness and good nature of most Dominicans.
This was the only book (or map) that showed the new road (highway 6 - opened late 2008) from Santo Domingo to Sanchez. This excellent road cuts a couple of hours off travel from Santo Domingo to the north coast.
We visited Santo Domingo, Boca Chica, Hato Major, Río San Juan, Cabarete, Sosúa and Puerto Plata as well as some rural areas. For the towns where the book provided maps, they were accurate and quite helpful. We drove about 550 miles and found the surface condition of roads varies from excellent to "You call that a road?" I don't think the DR infrastructure is sufficiently well developed to make timely repairs.
Driving around in towns provides much adventure. Street names may be present. Roads may be OK or extremely rough. You will surely find speed bumps and drainage ditches that you need to cross. (We put rain drains underground while in the DR, rain drainage is above ground and across streets especially at intersections.)
The Rough Guide points out that motorbikes (motochonchos) are common except in Santo Domingo. It is indeed true that if you are lost, you can flag down a motochonista (driver) and ask for directions. If he (only a few women) knows where it is, he will take you there and you are expected to tip him at the end of the trip. We did this at least 3 times and saved much frustration.
Both of the hotels we stayed at, Casa Blanca in Cabarete and Zapata in Boca Chica, are accurately described in the book and accurate maps accompany the town descriptions. We stayed in these two towns because we could explore the southeast from Boca Chica (as well as snorkel a bit) and the northeast from Cabarete. That worked well and the places we went to were accurately described in the book.
I noticed another reviewer was using this book as an inspiration for travel. I suggest another DR book, Adventure Guide- Hunter or one of the more superficial small books such as the Berlitz pocket guide. However, The Rough Guide is what you need if you are actually traveling to the DR. (I would have rated this a 4.5 but couldn't so I rated it a 5.)