Anyone who has rats, guinea pigs, or other assorted pet rodents in their home has almost certainly tried brand after brand of bedding in the hopes of controling smell, while still providing appropriate comfort and cleanliness for their pet. (A reasonable cost would be great too!)
After trying several brands of bedding, my family has decided on our favorite... the Carefresh Ultra bedding in bright white. It has an extra ingredient to help control odors and while no one will mistake the cage for a bed of roses ready for picking, I can tell a noticable difference in the level of smell coming from the cage. If we change the bedding fully every 4-ish days, there is nearly no offensve smell. Typically, it's more like once a week that the cage gets a full change of bedding and scrub down, so by that time there is a bit of an odor, but nothing like there was when we used shredded newspaper or some of the less expensive brands of bedding.
The only negative I have found is the cost. A 50 liter bag will run about $17-20, and for the size cage we have, it takes nearly a full bag per bedding change. That pushes $100 a month, which adds up quickly. That said, there is a slightly cheaper bag of regular CareFresh (not the Ultra) which saves a few bucks per bag, but does not have the odor control which really does make a difference.