Warning: If you plan to read or are in the process of reading Mistborn Era 1 do NOT read the below. If you have no idea what that means then read on, but it will probably make no sense to you.
After reading Mistborn Era 1 (The Final Empire, The Well of Ascension and The Hero of Ages) and what's out of Mistborn Era 2 (The Alloy of Law, Shadows of Self, and The Bands of Mourning) I have one nitpick and one question.
1. I feel that Trell should have been mentioned more in Era 1. It's mentioned twice - once by Sazed when talking to Vin and once when Sazed, newly Ascended, uses the recordings of the Trelagists to shape how the sky should look. Sazed also uses other religions to shape other parts of the world. I feel that it should have been mentioned just once more to give a hint that it's going to be used later.
2. Since atium and malatium were lost after Ruin's fall as they were part of Ruin's power, what replaced the two? Did cadmium and bendalloy replace them, since atium and malatium also were time-related, or did chromium and nicrosil replace them, since in Feruchemy they mess with higher powers?