When using the weapons optic, (default right click) from the gunners seat and then cycling through vision modes (default "N" key) when in WHOT mode text on the optic is white but when switching to BHOT mode, the text doesn't switch and stay white rather than black which makes very hard to read.
Compared to vanilla optics such as when using optics on the Wipeout, it's very difficult to see. Example pics, SU-34 BHOT top pic WHOT bottom pic
Also of possible note, all terrain is completely washed out with no definition, at least in the test I did. Could possibly be do to the time of year and map used. That being said, while in FLIR it's normal for the terrain to be obscured, it seems to be much more than in the vanilla assets.