Pros: No Smell in-and-of itself, Absorbs moisture well, Less dust, Hypo-Allergenic, Long-Lasting
Cons: Tracks about the same as clay litter, Drying on nasal passages if you breathe it in a lot, Pee does not clump
I made the switch from clay litter for a variety of reasons including less dust, less smell in-and-of itself, and I wanted a longer lasting litter. I love that I don't have to change the entire litter box more often than approximately a month (with one cat) or a couple to a few weeks (with multiple cats). One of my cats has chronic upper respiratory problems and this litter has less dust than clay litter. I've noticed an improvement in the consistency of his nasal discharge. With clay litter it was more sickly and cloudy looking than with silica gel litter.
I like the Ultra Pet Ultra Cat Litter brand, mostly because if you buy six bags of it and save the UPC labels, then send them in, they'll send you a free bag of litter! I think I like the pearls kind better, though, because the bigger particles track less and have less dust than the smaller particles in this specific type. I don't like that urine does not clump, but because it changes the color of the crystals, after a few weeks the color of the litter overall is changed and it lets you know when to change it. The good thing is, because the silica gels absorb so much moisture, the smell of urine is lessened considerably versus clay litter and it sticks to the bottom of the litter pan less than clay litter.
I wouldn't say it's perfect, but I like the litter and it's been working for me and my kitties for a while now and works better than clay litter.
By the way, if you have dogs, make sure they are not eating out of the litter box, because this type of litter is very drying to the mucous membranes of the mouth and nose if ingested, so you don't want them digesting it!