Right, I've been using the Seek Thermal XR (about £200) for autumn investigations on Bodmin Moor and wanted to give it a proper review since I see it recommended a lot on here.
The good: Excellent image quality, connects to phone (Android or iOS), battery lasts ages, intuitive interface. When you're out in November cold looking at stone circles, you appreciate something that doesn't die after an hour.
The bad: Heavy reliance on your phone means if you lose signal or battery dies, you've got a £200 brick. Colour palettes can be a bit washed out in certain lighting conditions. Needs a good few minutes to calibrate properly in very cold weather.
The paranormal-specific stuff: Is it better than a cheap £40 thermal unit? Yes, noticeably. Have I captured anything genuinely anomalous? No. Have I ruled out a lot of natural explanations for cold spots? Absolutely. If you're serious about thermal investigation, it's probably worth it. If you're just mucking about, save your money.
Overall: 7/10 for general use, 8/10 if you're doing serious temperature anomaly research.