Just a few days after hitting store shelves, Samsung Instinct has become the fastest-selling EVDO handset in Sprint history.
The Samsung Instinct was first available exclusively to current Sprint customers on June 19th breaking records for the initial launch of any Sprint product.

The record pace of Instinct sales has led to temporary shortages of the device at some locations across the United States. Sprint and Samsung are diligently working around the clock to increase inventory in all sales channels. Samsung has increased efforts to deliver new supplies of Instinct on a daily basis and manufacturing plants are operating at full capacity to keep up with the demand.
Sprint did not disclose any specific numbers on the Instinct sales. Not telling any numbers reminds me of the whole Amazon Kindle controversy. It was sold out, but nobody knew how many Amazon actually made available initially.

Instinct costs just $129.99 with a two-year contract after a $100 mail-in rebate.
See also the Sprint Instinct site.