I did read Secret History, even though I read that it had spoilers... it said minor spoilers, so I figured it would be okay, though since I haven't read era 2 I'm not entirely sure how spoilery it is. ^^; Regardless, it was so good and hilarious I think it was worth it, and I think it was better for having just finished HoA a few days ago.
I'm debating buying AOL on Amazon or seeing if someone I know has it, or even pulling something crazy and listening to it on audiobook since my dad has it. Ironically, I have a copy of Shadows of Self already, which I got for my dad at a midnight release, signed and everything, when the only Sanderson books I had read at that point were Steelheart and Firefight. XD (He didn't care about it because it wasn't an audiobook, so I got to keep it.)
The only Arcanum stories I haven't read are Emperor's Soul, Sixth of the Dusk, and Allomancer Jak.