I used the second edition at my small seder this year. I describe this seder as the "it takes as long as it takes" seder, encourage lots of discussion and Q&A, and ask everybody to bring things to share -- teachings from other sources, their own insights, new melodies, poetry, whatever. My guests obliged and there was much discussion.
I gave everybody a copy (to take home later) at the beginning of the seder and saw people paging through it while we talked. Other haggadot were being passed around too. I referred to Hagada - Mi Yodeya? for at least the following topics:
"Does everyone wash?" - indirectly, when we got to Rachatz and had a quick discussion of who was or wasn't getting up to wash.
"What does the word 'karpas' mean?" - our haggadah had mentioned the connection to Yosef's garment in passing, and I read from the answer here for more detail.
"Why is the wicked son sanctioned...?" - in passing, as part of a discussion on that topic that someone else initiated.
"How do we know the wicked son would not have been redeemed?" - in passing, as part of a discussion about many Israelites not leaving and how avoidance of the final plague required positive, public action to identify with Yisrael. (I don't quite remember how this all came together.)
"Did hardening Paro's heart mean he wasn't really responsible?" - I read the majority of Jake's answer about God influencing people without taking away free will. This seemed to be well-received.
"How would Har Sinai without Torah have been enough?" - I shared the gist of Alex's answer after somebody else brought this up.
"Hardboiled eggs and salt water?" - used this information in passing.
"What do you do with the Kos Shel Eliyahu?" - I remember this coming up but I don't remember the details now.
The two Chad Gadya questions - mentioned the questions in passing but we didn't discuss.
A guest commented on "What do the haggadah section titles mean and where do they come from?", and another guest said "I've always wondered that too!".
We also had a longish discussion of arami oved avi, during which we consulted Rashi, a lexicon, and several other haggadot. All the time I was thinking that I should ask about this on Mi Yodeya, though I think we managed to round up most of the main sources already so I'm not sure if I still have a question. Maybe I'll ask and answer it. It's something that I would have liked to have in Hagada - Mi Yodeya? but I hadn't realized this until we were in the midst of the seder.
Addendum: it turns out somebody already asked that, but because it was asked as a question about the parsha rather than a question about the haggadah, we didn't consider it. When we do a third edition we should review questions on the parshiyot quoted in the haggadah to see if there's anything else we should bring in.