The higher the frequency, the less penetration of solid objects you have.
At -that- frequency, it'll work well for extremely short range, indoor, communications. But as soon as you put something even slightly solid, or damp, in the way, the signal will get blocked.
Yup. At this frequency, walls and vegetation are essentially opaque to RF. This will be useful for in-room or sub-kilometer line-of-sight deployments. Great for Phoenix (little rain, few tall trees), horrible for Seattle (damp, heavily forested).
One good thing about hitting 25 GHz or higher is that indoor APs and outdoor APs don't fight with each other the way that they do at 2.4 or 5.8 GHz (lower co-channel interference). So you can have a PTMP or mesh network running in dense areas like New York City. But with the range limitations, it'll need to be a dense network in order to get any sort of coverage. Your hop count is likely to skyrocket if you're using a mesh. High speed, horrible latency.