Runamuck, from your front brake description you definitely have a bent disc causing the surge you feel. Question is, are one of the discs bent or are they both bent? Unless you can determine this yourself with a trained eyeball and a fixed piece of wire or a dial indicator you may want to let your dealer check it. If one or both are bent you need to figure out how they got that way so it doesn't happen again. Are the discs discolored from overuse? Perhaps the last owner changed the front tire before he sold it and slightly bent one of the discs during the change? If this is the case you can usually find a ding or scuffing on the outer edge. If it's only slightly bent a good mechanic can actually straighten it if he's willing. Most dealers would prefer just selling you a new one. Just get it straight, make sure you have good OE pads and enjoy your ride.