I saw the show last Saturday (which was still technically a preview), so I feel I can comment on this one. First, I saw Idina in the show in NY with JLT, twice, and really, its hard to compare. Idina's acting and vocal ability is just mind-blowing, so really, after that, anything else is going to be second in comparison. With that said, Eden was good. She will be great, but I think she has to get used to being back in the role. She started off a bit weak, but I attributed that to the fact thatit was only her second performance in Wicked in SF, and after a long break, right? I didn't care much for how she pronounces gravity in Defying Gravity though because you can tell she's doing it so she can hit a certain note. Don't know how to quite explain it, you just have to hear it.
In short, she was good, and will most likely improve as the run goes. Her Defying Gravity belting was good, and by the end of the show she seemed like she was more into the character, acting-wise and vocally. I have to admit though, I wish I had seen Stephanie Block to comare as well because I heard she was extraordinary.
My two cents!