What fails more frequently: hardware buttons rated at a hundred million presses, or software written in Java?
In the case of the Nexus One, the power button is a huge weak point. Mine hasn't worked in 5 months.
Yeah, Apple got this one right. No matter what you do with your phone, you can just press the big black button and everything is back to normal. If anything, I think these software buttons will lead to further user frustration.