[Closed] Rough, squeaky front brake

I've got a set of Shimano LX disc brakes, which are great. The stock Shimano organic pads that were included have been very quite is use, with a slight 'hiss' as the pads contact the rotor and the rotor runs through. Unfortunately I managed to contaminate the front pads with some suspension oil and due to the huge prices of Shimano replacement pads (and after some advice on here) replaced them with aluminium backed A2Z pads. The A2Z pads are supposedly a 'special' organic formulation.

Now, in use, the front brake squeaks and feels rough, almost 'gritty' (to the point of almost feeling a bit juddery), although it appears to stop the bike. The rotor is clean and true and spins cleanly between the pads, the caliper in centralised (equal gap on each side and the pads appear to hit the rotor at the same time without and real, apparent rotor bend); the brake just feels rough as is noisy.

Have I done anything wrong or is there anything I should be looking at, or is it just a case of a different feel to a different manufacturer's compound? I've not ridden many types of brakes and pads.