Sensor is low res and by using Flir Tools, you can see raw sensor data. Definitely a lot of bleed due to the small pixel size.
Going to the Flir One App itself, it's obvious it is applying several filters to squeeze more detail from the soft source image. This results in decently sharp images at the cost of overshoot/ringing on hard edges. Quality degrades severely when moving, so a lot of frames are being combined. Possibly superposition and compositing as well to increase resolution.
There is a massive amount of lag. About 1-2 seconds when previewing, and 2-3 seconds when recording video. Extremely irritating. My phone is a 3 month old Google Pixel that is definitely no slouch. I'd blame the (probably) SoC running linux inside the dongle adding unnecessary overhead.
It is *required* to create a user account to use the program. Even worse, to use FLIR Tools, you must create a *second* user account, both of which require E-mail validation. App is buggy and randomly quits working. I had to reboot phone to be able to save images.
Low temp/narrow span is very good. Much more usable than the NEC Avio. That's really the only pro though. Wide FOV, fixed focus means this is useless for PCBs.
Is it a good deal for $400? Maybe. The non-Pro version with the 80x60 sensor is half the price, and about as practical if you just want to find obvious problems. If you want nice images you are barking up the wrong tree.