My set arrived this morning!
FedEx got it to the door at 10:30 AM and the box showed no signs of damage whatsoever. It was a quick drop and run, by time I made it to the door he was already on to the next house.
Unboxing setup and YouTube 4k:
Thinking the back light bleed may have something to do with fragile bezel design (or cheap construction of the casing in general), I took my time unboxing and was very careful when moving the set once unboxed to it's final destination. This is a 50-lb+ set and the frame is a rather thin plastic. i could see how too much pressure on one of the edges could cause a small crack. So although it should go without saying, give your new TV the same careful white glove treatment a pro would.
Got it setup, connected to WiFi, etc... First 4k content I viewed was on YouTube. Started with the "Vertical Maze 4k Dubi" skydive video (screen shot below, the room I have this set in has a lot of light in spite my closing the blinds or I'd take more). From there I went on to check out several 4k movie trailers on YouTube. Blade Runner 2049 (highly recommended), Thor: Ragnarok and a few others. I'm very impressed with the performance in terms of WiFi connectivity. I remember it bring reported that 2016 TCL sets have had issues in this department so I was worried about streaming over WiFi but all seems fine.
Most YouTube videos appear to start in 4k, but a few start in 480p and then quickly scale up to 4k. I'm accustom to this as YouTube's HD content on occasion behaves the same way, starting low res then converting once a small buffer build. Once the 4k videos transitioned to 4k I got no lag or video hiccups, just smooth 4k playback. I can provide broadband speed test results if requested.
On to Roku apps:
I upgraded my NetFlix account to support UHD content and then signed in and previewed a few offerings. Then I moved on to Vudu. This is my first time to use Vudu and I'm impressed with the selection of UHD 4k and Dolby Vision support. It seems several rentals are only $0.10(!?!) and several movies are free with adds on this service. Although the UHD movies are a bit pricey to rent some of them like Batman Vs Superman and Lego Batman allow you to watch 10 minutes of UHD 4k preview footage for free.
Proceeded to pop in Digital Video Essential: Basics calibration Bluray and performed brightness and contrast test. Contrast seems perfect at factory default (100%). I raised the back-light up to 27 from Movie mode's default of 20 and I'm wondering if I can push it up a bit further as the room can get bright and I do some day time viewing. With backlight at 27, I'm keeping brightness at 52 and calibration patterns are telling me that's correct. I am curious about settings others are using in bright rooms. My colorometer doesn't do wide gamut so I can't run any test in HCFR, but since all my displays are calibrated I pulled up a few frames on my old TV (which was calibrated in the same room) and compared the same frames on the 55P607 and I'm very happy with the out of the box color. This is probably the first set I've purchased where I'm content enough with the out of the box warm setting to leave it be for while.
Problems and overall sanctification:
The room is too bright to make a call on potential backlight bleed but I'm not seeing any signs so far. To try and get a dark environment a put a blanket over the back of the TV building a little tent of sorts and put up a solid black image with a few white rectangles in center. Corners all look uniform. I don't want TV in complete darkness, we always have a few dim lamps on even at night so even if there is some bleed (and again, I see none right now) it probably won't be a deal breaker. Also ran a few dead pixel test panels and I'm not seeing any problems. I'll also parrot what others have said about Roku software, it's excellent. Also really love the headphone jack on the remote, tested this and audio is clear and no sync issues. Overall very, very happy with this set so far and my experience with it is exactly as expected based on the three reviews I read.
If I have one negative comment it would be that I wish TCL would have provided a simple daytime/nighttime settings toggle button on the remote. It was a common feature many years ago and it seems to have gone away.