I like that it integrates very well into our existing infrastructure, so there are few customizations needed for other applications as opposed to having an entirely new one built from scratch which would be more costly in time & money.
The support team can take some getting used too - we had issues when trying out something simple at first but then were unable to resolve them after calling (which doesn't help). Also their implementation of SSO was not working properly until they made changes themselves. As stated above this integration works great! We've been able to reduce the amount of tickets/issues we're dealing wtih by 50% since implementing OpenAthns.