We had the AOS interview for my mother today, February 27 2009, at Houston office.
I accompanied her as a translator and petitioner (no questions were asked about that). The whole interview lasted 10 minutes, just several questions about some points in the forms.
The officer explicitely said: "parents' cases are easy". Well, he also said "so, she came here for a visit, liked it and decided to stay - ?" and sounded a bit sarcastic. I answered that no, it was her 5-th time visiting, no initial plans to stay, but our situation changed during her visit (we found out we'll have a kid), and that triggered her to stay (my mom overstayed turist visa, before I got my citizenship; I applied for her GC in September 2008).
The officer did not ask for any document (exept my mom's pasport). He did not take away anything either (like my mom's EAD). He told the greencard should arrive in the mail in about 10 days.
So - good luck to everybody.