It turns out that the PS Vita's CPU is clocked slower than we all expected (something in the ballpark of 800MHz).
However, Sony made the right decision here -- it's in everyone's interests that the Vita sustains that maximum performance over lengthy play sessions, offering great battery life to boot. This should be applauded.
The PS Vita's CPU speed is clocked at between 44-444MHz.
The 800MHZ figure stated was the expected figure from many years back. Sorry about the confusion.
Do click through to the piece for the details, as Sony's decision to set the maximum speed to 444MHz is actually pretty smart.