I don't think it hindered hardware speed.
The only place where it demonstrably held back hardware performance was AMD dual-cores 2005 - 2006, and AMD quad-cores 2007 - 2008. Both scheduler design flaws in Windows that AMD had to patch themselves to limited effect (the first case) or had to remove a feature from the next generation to fix it (second).
First - AMD dual-cores were slowed down as the scheduler didn't use both cores effectively. Required the 'dual core optimiser' patch but even that didn't fix it entirely.
Second - Independent clocking of cores on Phenom I again led to the scheduler not utilising all the cores properly. Was removed in Phenom II.
...I suppose you could count the lockout of BeOS in the 90s and Linux in the, uh, 00s from OEMs meant that non-Intel processor architectures couldn't get any mainstream support. But Intel and AMD provide enough competition and performance increases that it hansn't mattered.
