Few detergents products with a radically different design can match the cleaning ability of standard powders/liquids.
According to Consumer Reports, the new Purex 3-in-1 sheets are dismal cleaners. Remember the Oxi-Clean detergent ball that was supposed to last for 50 loads? I tried it and it worked well on stains like Kool-Aid, but couldn't touch anything involving grease.
Put me in the skeptic column.