I've been recommending Costco pharmacy for nearly 10 years to family, friends, co-workers, health care practitioners and persons waiting in line at queue at the bank, post office and grocery store.
Costco has consistently, reliably, promptly, accurately and economically filled and refilled my prescriptions that entire time. I'm vastly more satisfied and impressed with Costco than Walmart, Walgreens, CVS/Albertson's, Safeway or Target.
The generics they provide are consistent for years at a time, avoiding the variations and issues that can arise among generic manufacturers.
Fulfillment is much faster than promised. The claimed processing time is 4 days, with 6-day shipping at no additional charge. Products consistently arrive in 5 days total, occasionally less.
Prices are competitive with any online supplier, and usually lower than any of the brick-and-mortar pharmacies.