I've used the same technique as Sveta for years on all kinds of cashmere and wool sweaters without any issues. Cashmere gets beautifully soft and smells heavenly if you home launder it. My husband wears his cashmere sweaters daily around the house once he realized that he didn't need to worry about sending them to the cleaners.
The only time I'd hesitate is if the item was heavily embellished or if it was a very open, lacey knit. Even then, I'd probably do it at home because I would just be extra gentle to avoid stretching out the item or damaging the embellishment.
If you think about what happens in most dry cleaning establishments, you'd probably get over your worries fairly quickly. The thought of my cashmere sweaters tumbling around in a chemical bath with other people's dirty clothes makes my gentle soaking/ rinsing/towel drying/flat blocking to air dry method seem pretty benign.
ETA: Oh, and if your cashmere doesn't feel soft and fluffy after hand washing, it's probably because you didn't rinse out all the soap. Just a drop or two of soap in a sink full of tepid water is usually enough to clean the sweater and it's important to make sure you rinse out all the soap before you towel dry and block. I use a supposedly no-rinse, made-for-wool product called Soak but still rinse to make sure the sweater is free of any detergent.
