Deliverr.com is based in California with a few warehouses on the West Coast. They provide nation-wide network and specialize in providing 2 day fulfillment to your customers.
Usually bad reviews come from 3 things;
Difficult user experience
Complex/expensive rate structure
Deliverr is easier to use than normal 3PLs, even the large ones, thanks to their all-inclusive and transparent pricing (only 2 fees: fulfillment & storage), a focus on fast-shipping, and an easy onboarding (integrations with listing tools like Sellbrite and Channel Advisor and Shopping Carts like Shopify)
Make sure you understand their inbounding requirements and product restrictions - they are pretty unforgiving if you do not comply.