What’s the most frustrating part of interpreting an FTIR spectrum?

I’ve used FTIR extensively in materials analysis and I’m curious how other people approach spectrum interpretation, especially when dealing with an unknown material.

There are plenty of correlation tables and spectral libraries available, but I often feel that the difficult part isn’t finding a wavenumber in a table — it’s deciding which peaks actually matter, recognizing patterns, and avoiding over-interpreting individual bands.

For those who regularly use FTIR: what part of spectrum interpretation do you find most difficult or time-consuming?

Peak assignment? The fingerprint region? Distinguishing similar materials? Identifying contaminants? Knowing which peaks are actually diagnostic?

And when you’re stuck, what do you normally use — spectral libraries, literature, correlation tables, software, or something else?

I’d also be interested to hear whether your approach differs between academia and industry.