I just ran an analysis of my apps and the fastest was 8hrs (June 20th) but since then it's been trending upwards with my last 3 updates coming in at 40hrs, 67hrs, and 98hrs. These are all my apps, the company I work for has at least 2 recent updates that took over a week. That's just absurd.
If the App Store can commit to 24hrs being the max time then maybe I'd be interested but for the foreseeable future I'll "Settle" for instant updates when I have a fix ready instead of waiting on Apple. Especially with how random approvals are (not just the time, the approval itself), I'll ship a tiny fix and App Review will kick it back for some native API I've been using since version 1 that they now want more info about. I don't fancy having my businesses at the whim of Apple Review.