I use a Belkin PF60 more because I like the look, pure eye candy, and can monitor the voltage fluctuations in my area than any benefits I have seen or heard.
I also use the Belkin PF60 although I found it for $149 (nowhere near that $599 MSRP). I bought it because we frequently have electrical storms and I thought that it might protect my AV equipment a little better than your average surge protector. One thing that is nice is that when there is a power surge the Belkin cuts off the power to my equipment until I reset it. It has done its job at least 3 times in the last two weeks.
