Flash PM Rob Christensen clarifies:

The final release of Mac OS X Lion (10.7) provides the same support for Flash hardware video acceleration as Mac OS X Snow Leopard (10.6).  The previous “Known Issue” described in a tech note suggesting that video hardware acceleration was disabled in Lion was incorrect and based on tests with a pre-release version of Mac OS X Lion that related to only one particular Mac GPU configuration.  We continue to work closely with Apple to provide Flash Player users with a high quality experience on Mac computers.