1) What have you learned about Illustrator?
I've learned that it is very similar to Photoshop, but it is very different when it comes to use case. Depending on what you are going to use it for, you should only use one, and shouldn't switch between the two. 
2) What do you like about illustrator?
I like that it is pretty straightforward, and makes a lot more sense when it comes to tools. It makes it a lot easier to find the tool I want, unless I am looking for exactly the right tool.
3) What about illustrator do you struggle with?
I don't really like the layout of Illustrator. I thought it was too simple. I like Photoshop a lot better (This is why I don't do iPhone), because it gives me the perception that I could do a lot more with it.