I don't have a 19 Classic, but i do have the new 66 2.75". I also have my old 4" 66-2 duty gun and my 66-2 3" that was used in Detectives by my brother-in-law. I love the 66-2s, but I've got to say that the new 66 is extremely accurate and reliable. I've shot quite a few rounds through it so far and have had zero problems. I have to say I'm hesitant to shoot much .357 through the 66-2s because of the forcing cone issue. After all, barrels don't grow on trees. However, the construction and advancements in metallurgy have made me quite confidant that the new 66 will hold up to .357 just fine.
I've got to say, though, the new 66 and the Classic 19 will never replace the originals in my mind. The new guns have some advantages, but they just aren't the same.