I have adopted 2 pets from the SPCA and have been very pleased with the entire experience.
It cost approximately $100 per cat. That includes shots, feline leukemia testing, and spaying/neutering. If you were to have all things done to a pet on your own, it would cost a lot more than $100.
The shelter gives you honest information about pets you're interested in. They will not conceal behavior problems.
They take good care of the pets. The staff are caring and affectionate to the animals.