A cathedral wall of west-facing glass is the reason you bought the lot and the reason the great room hits 84 degrees at four in the afternoon. 3M's Night Vision series rejects up to 72% of solar heat on the darkest shade and 99.9% of UV across the line, and it does it without the mirrored exterior that made older solar film wrong for a residence.
The winter half of the equation is the one nobody sells you on. Low-emissivity film reflects interior heat back into the room instead of letting it radiate through the glass. The same coating pushing summer sun away is holding your woodstove heat in during a January cold snap. In a mountain cabin that runs both extremes, that's the whole argument.
UV is also the fastest way a floor goes pale. Blocking 99.9% of it is the cheapest insurance available on a hardwood floor or a leather sectional that cost more than the film job.
One caution: not every film belongs on every window. Insulated glass units and low-E glass have specific film compatibility charts, and the wrong pairing can void the glass manufacturer's seal warranty. Checking that chart before quoting is part of what an authorized dealer is for.