The members of Cruise Critic offer many reviews of Transatlantic cruises on the Queen Mary 2. Nearly all of these passengers give the ship and voyage the highest marks. Kudos to the staff of the QM2.
CruiseCritic has many more reviews of Transatlantic cruises. They literally have hundreds of reviews about a variety of cruise lines, departure ports and itineraries.
At CruiseReviews, John has posted a Carnival Transatlantic cruise review. He sailed on the Carnival Liberty from Rome to Miami in October. He liked the food and cabin, but was disappointed in the layout of the ship.
A man from England offers a review of a Celebrity Transatlantic cruise. He took the Celebrity Millenium from Barcelona to Fort Lauderdale. The food, cabin, and ports get praise.
SeaLetter has a Star Clippers Transatlantic cruise review. William took the cruise from Spain to Barbados in October and says he'd go again "in heartbeat."
Read the long and detailed review of Royal Caribbean Transatlantic cruise from England to Boston. It's on the CruiseDiva site and is written by Mary and Vincent.
Here's a Royal Caribbean transatlantic cruise review by Jim. He was on the Splendour of the Seas and gave it a mixed review. The value was good but the food quality and disembarkation in Galveston left a lot to be desired.
About.com has 5 reviews of Transatlantic cruises. They're about the Cunard and Royal Caribbean cruise lines.