I own an Alienware M11x with the GT335M and Optimus, and have had no problems except on occasion running into a game that doesn't automatically start the 335, but that can be set manually in the driver control panel. Otherwise, no issues at all. I wouldn't worry about newegg reviews, they're generally misinformed and not representative of power users' experiences with products.
EDIT: After seeing one of the reviews, it is true that Optimus won't work with browser games unless you have the GPU active any time your web browser is open. But please tell me you don't play those browser games anyways...
