I have been running with BC coilovers on my MY05 STI for about 3 years now and have had no problems.
I had went through 2 sets of OE struts in the first 3 years.
I would not say they are the "best" coilovers you could buy, but for the price i.e. value for money you cannot beat them.
I have the 6/5 spring rate (6 front/5 rear)and on the softest setting they are about the same as OE shocks/springs, about 5 clicks hard is about the same as OE shocks/prodrive springs.
The coilovers have 30 clicks soft to hard so plenty of scope to firm things up.
Would advise to get the extended adjusters for the rears if you go this route.
Also I know of a low mileage set of BC's for sale for New Age STI with 114.3 PCD if that is the age of your car (MY05 - MY07 STI) if you are interested. (not mine by the way)