I asked this question before. I would like to know if things have changed with regard to 2D and 3D hardware acceleration under X.
Question: Is is it actually possible for two or more simultaneously logged-in users to benefit from 2D/3D hardware acceleration?
Test Scenario: I create two user accounts, user1 and user2. I log in first as user1 and then, without logging out as user1, also log in as user2 (double emphasis on the word "without"). Only the first user account, user1, will get hardware video acceleration. The second user, user2, will not get hardware acceleration. For user2 to get hardware acceleration, it's necessary to log out user1.
It appears that as far as hardware acceleration is concerned, X is still a single-user system.