Here are a couple reviews that I've noticed around the net:
Gamespot gives C&C 3 a 9.0:
Regardless of your history with Kane and his cohorts, Command & Conquer 3: Tiberium Wars is one of the finest real-time strategy games in years. It's also a triumphant return to form for the series, because it's more than just a graphical update--it's an exciting, well-tuned experience with enough that's old and enough that's new to thrill old-timers and newcomers alike. Suffice it to say, you should play this game, and expect to be playing it for a long time to come.
IGN gives C&C 3 an 8.5:
Add models that are clean and crisp, even at an infantry level (not something they got right in 2003's Generals), and you've got a beautiful game. When two large armies come crashing together in the middle of a battlefield, it's pretty hard not to be transfixed by the incredible fireworks display. These visuals many not make a difference to the hardcore that only care about unit stat differentials and build times, but the general public will find that this is one of those titles that becomes more fun because of the quality of the visuals working together perfectly.