There are actually 2 blocks - first, the decocker doesn't drop the hammer all the way so it can hit the firing pin. It stops half way in between. Then the firing pin also has a separate block, so it can't be pushed forward unless the trigger is pulled back. It's a little unnerving to watch the hammer drop when there's a round in the chamber, but it's safe.
As for finish, the stainless steel slide wears much better. When the edges wear, there's just more stainless steel underneath, so you can't see any difference. But it does still show light scratches, they're just the same color as well. But I still like your basic black better than twotone, but that's just me.