As expected by anyone with more than half a brain, Apple has not been engaging in tax evasion, here or anywhere else, and only seeks to avoid paying the full U.S. corporate tax rate of 35% on funds earned and already taxed outside of the country, just to be able to bring those funds here. Quoting from Apple's official position document,
Current US corporate income tax law severely discourages the use of these funds in the US by imposing a 35% tax on repatriation. Having been singled out for criticism on this issue, Apple is taking advantage of the platform they have been handed to push for corporate tax reform. The company's official position is available as a PDF.
Update: The Senate Permanent Subcommittee on Investigations has issued a report which tells a very different story, and for which that committee is very likely to soon be sorely embarrassed, as the weight of public opinion shifts behind Apple.