From what research I've done on other forums, the bag of pellets you get may not be enough if you have a cat that likes to dig to China. People end up using 1 1/2 bags, which means the monthly expense goes up. You cannot use two bags if you have a cat who really likes to bury as the urine won't drip down through to the pad correctly if there are too many pellets.
Also, some pellets do stick to the poo, so you lose some as the month goes by and have to replenish.
As for the pee pads, if you have a cat that likes to pee in one spot, you have to open up the tray and turn the pad around or the pee will oversaturate that one spot and leak all over the tray.
I heard the pads are the biggest expense. And they are quite stinky as you pull one out to change.
People on other forums have said that when their cat totally didn't adapt to the Breeze system, Tidy Cat did refund their money. When I called a while back with a question about the improvement in their scoopable litter, I asked the CS guy about the refunds for the Breeze and he did say he would refund my money if Kitty did not use the system.
That was a while ago. I don't know if they still do that. But, it also tells you that they've had quite a problem with cats unable to make the change over so they've had to offer refunds... Or, I just realised, it could also mean so
few cats have had problems that they were willing to make a refund for the few that do.
Also, since most cats are finicky about litters anyway, I don't know if it's a higher percentage of them not using the Breeze system over anyone trying to get their cat to switch to any of the pellet-type litters, like Feline Pine or the paper pellets a PP mentioned.
I don't know how she avoided getting her pipes clogged up.
and doing the recommended 3 litterboxes for two cats, we figured the $30 initial investment was worth a try. I also agree "pellet poo" WOULD probably be pretty disgusting, so I'm just as happy they only use it as a urinal. But it's worth it to cut back to two litterboxes - Breeze for the urine, and a normal litterbox for poo. 
But after acquiring an early generation bengal and almost putting him down because of MAJOR diahhrea with commercial foods, we tried a raw diet as a last resort with an amazing side affect: virtually odorless, solid stools.
But it appears the high quantities of corn, corn products and other grains used as fillers in commercial foods (NOT naturally a part of a cat's diet) are the culprits. Perhaps avoiding those would help reduce the "smelly poo" for your "normal" cats. 
