I'd say reliable and cheap but realistically it would depend on your definition of cheap and your definition of fast.
a pwsc'd focus is a billion times better than a stock focus in power however you're still going to get hassled by relatively stock stage 2 subaru's evo's mazdaspeed3's and well built stock turbo 1.8t vw's and wrx's
its cheap for a full boost setup definitely, but for someone whose got say a $4k focus it's more than half the price of the car.
IMO the powerworks is one of those "the sum of its parts is greater than its whole package leads you to believe"
the blower whine, instant torque and dead nuts reliability of the kit makes me miss my pwsc all the time (not the car it was on though because goodnight that focus was a lemon!)
'03 VW Jetta TDI
'02 Chevy Corvette Z06
'87 BMW 325e