I did. As with all Lepin, there are a TON of unmarked bags. So you need a lot of sorters and space to work. But brick quality was very good, no missing pieces, etc. I spent several hours over the Labor Day weekend putting it together.
I've seen Stan Lee customs, but never a bootleg. I really hope that's legit. (I bought an extra Alfred from the Batcave set to try to make my own Stan Lee, but this would be way better.)
I haven't seen the hulkbuster sold separately. However, you can get any of the sets (SY 357, Decool 7110, Lele 79081, or XINH 8019) for around $12-$13.
I have several lepin sets and none of them made me itch putting them together. But YMMV. I also don't play with them much after building.
At chinese toy fair, Lepin also had new ghostbusters firehouse set and classic batcave. Looked like they just put their sticker on the actual lego box, but hopefully we'll see them soon.