I thought it was...okay.
Gillen did a serviceable job but at times it felt like his heart wasn't in it compared to some of his other titles. I feel like part of the problem was Gillen being more at home with titles where he can go more "indie" or creative compared to Iron Man, where it felt like it was too mainstream for him, if that makes any sense.
The adoption retcon, which was probably the biggest thing he did on his time on the book, being an issue or not is probably dependent on the person, but personally I don't think very much good has come out of it in the long run aside from Arno Stark.