according to industry estimates and HP press releases. In contrast, Apple had sold 2,000,000 Ipads in the first two months of sales, and will sell approximately 10,000,000 in the first 3 quarters (constrained by Flash memory availability). Projections are that they will sell 28,000,000 in 2011.
Windows alternatives perform the same job as the Apple equivalents, just as a Ford Focus will perform the same job as an E class Mercedes or a 6 series BMW. Some people see the value in one execution, others see value in the alternative. Some can't see the difference.