My experience with passport renewal (still in progress) differs significantly from those recently reported in this thread. Last July 21 I sent in a DS-82 renewal, submitting an up-to-date photo with a freshly expired passport, and requested a 52-page book and photocard. When I had heard nothing by August 12 (last Saturday), I checked online, where my application had a locator ID but no information on where it was in the process. I also haven't received any emails advising me of application status.
A few hours ago (today, August 14), I called the National Passport Center and was informed my application had entered the system on July 26 and was with the Washington passport office. (I had mailed it to Philadelphia, which is the designated reception point for Kansas residents.) As of the time I called, neither the new passport book nor the card had been mailed to me. I ended up paying $75.45 by credit card to have my application expedited, since I am leaving on August 22 for a driving trip that involves a crossing of the Canadian border on August 25.
I am not sure why my application is so delayed compared to others'; I have had no name changes, and although I did not specify travel dates on the application, I have applied in the past without travel dates and still had a three-week turnaround with routine processing. There were three main differences this time around: in 2007 I applied just for a regular-sized book through the US Embassy in London using DS-82 filled out using the free-text function in 'Acrobat', while in 2017 I applied domestically for both an extra-large book and a card, using the State Department Web form to autogenerate a PDF (which changes lowercase email addresses to all-uppercase).
I actually had DS-82 ready last March but procrastinated because my initial plan was to take my own passport pictures, with the help of a friend, using an improvised home studio setup. I had had to do this back in 2007 since I was living in Britain, where passport photo standards are not compatible with US ones, and I felt the DIY process (with the help of 'Photoshop') resulted in better photos at lower out-of-pocket cost (35c for two 2" x 2" photos cut out of a single 3" x 5" print with scissors, Exacto knife, or lever-arm paper cutter, versus $15 for two prints from Walgreens or a competing drugstore with photofinishing services). However, I never got around to this project because my current house lacks a well-lit bare wall painted in a light solid color to serve as a backdrop.
My advice to anyone similarly situated, with a tendency to make the perfect the enemy of the good, is to get the complete package sans photo ready to go (envelope, old passport, DS-82 filled out with date and signature, and check or money order), and then allow just one week to obtain DIY photos. If the week passes with no progress, then if the Walgreens near me is typical, you should be able to walk in with $15 and walk out less than an hour later with two photos that meet the State Department's size, pose, and illumination requirements. If your passport photo shows you with bed hair or suggests you are in the final stages of meth addiction, that is still better than paying half again to double the routine-processing rate for current and universally accepted proof of identity and citizenship. It also leaves fewer opportunities for mishap to have passport already in hand than to try to coordinate renewal with other travel planning.