I thought I would share my thoughts and experience with the different brake pads that I have used:
Stock Subaru: $400
Ferodo DS2500: $300
Hawk HP+: $200
Just before I stared autoxing I needed new pads. The stock set had lasted me about two years with only street driving. I called a dealership and they quoted me the $400 for the set and tried to get me to come in for a full brake job for $1000. I passed on the offer.
After a few recommendations I decided to go with the Ferodo DS2500's. Considering that they are a better pad for autox and $100 cheaper I was happy with the idea. When I got them from KNS I found that two of the pads had been damaged inside the box. KNS got a new set right out to me just in time for the fist event of the season. As one would expect, these pads made a bit more noise and dust but had a much improved feel to them over stock. They also lasted about as long as the stock pads but this time they served as DD and autox pads so I was very happy they held up so long.
This spring while prepping the car for the beginning of the 2011 autox season I found that it was time for new pads again. This time I decided to try out the Hawk pads. I spent a little time trying to decide between the HPS and the Plus, and decided that I don't use the car for a DD as much any more that I should go for the more aggressive ones. I also replaced all four rotors this time around with new blanks. I have been using these pads for a few weeks now and couldn't be happier. Yes they are even louder and dirtier than the DS2500's but they feel even better as well. This could be partially because of the fresh rotors though. I think these pads would be overkill for people who only use the car on the street unless you get cut off as much as I do here in MA, then they come in pretty handy!
*Update*: After a few autox's this season I am really loving these pads. They stop amazingly! I even had a chance to let someone else who had autox'ed my car before, take the car for a run. He was hugely impressed with the improved stopping power, so much that he may be getting some HP+'s for his car!
Oh, and on a side note, I have only snapped one caliper bolt off to date and was lucky enough to be able to drill it out and save the threads. Always use anti-seize!!