About 9 days (including weekend) between application and conditional approval for me (GC holder, which may or may not speed things up, as they already have a recent background check on file).

Lucked out with interview. My nearest regular interview location is a few hours' drive away, and all the airports with GE offices that I would fly through over the next few months were booked up through August. But I noticed an interview site in my town listed under the 'Invitation only' section of the schedule screen. A quick google search showed that CBP was doing a two-day popup interview stint 5 minutes from where I live -- starting the day after I got my conditional approval. So time between conditional and final approval was something like 15 hours.