The problem I had with the Seek model was that it connected to my phone via a Lightning connector, and there was no good way to ensure that connection remained solid. Dropped the thing the same day I got it, and it broke. Haven't tried one since.
It's also hard to use them if you have any kind of a case on your phone.
If I had one that worked via Bluetooth or Wifi, or was built into a phone case, or had a longer cable that I could route around my existing case, then I might give it another try.
Short of that, I'm looking forward to the standalone model.
Re: camera built into phone case, also worth mentioning that the very first version of the FLIR One was a camera integrated into an iPhone 5/5S case. The obvious downside of this is that if you replace your phone with a new model you can't use the camera anymore. This particular design may have a second lease on life if you go to an iPhone SE, but a lot more people moved to the 6/6S/7/7S which won't be compatible.
Standalone versions have been around for years with a really wide array of designs for different purposes (industrial, security, testing, most recently lightweight UAV cameras). For the standalone cameras you pay a bit more because it can't bum off the phone's screen, storage, input, and all that. The TG165 at $350 looks to be the low end unless I'm missing something. No way to browse their site by prices.
It's also hard to use them if you have any kind of a case on your phone.
If I had one that worked via Bluetooth or Wifi, or was built into a phone case, or had a longer cable that I could route around my existing case, then I might give it another try.
Short of that, I'm looking forward to the standalone model.