Absolutely true. Phenylephrine liquid applied directly to nasal mucosa is a quick and effective decongestant. It doesn't last as long as oxymetazoline (the other big nasal spray ingredient), but it also doesn't cause you to become dependent on it as much as oxymetazoline does.
Nasal phenylephrine is a miracle when I am trying to sleep with a stopped up nose. A spray in each nostril and my nose is clearer than even normal within a few minutes.