Overview of Find features:
http://find.episerver.com/ and http://world.episerver.com/Articles/Items/General-Availability-of-EPiServer-Find/

Overview of EPiServer Full Text Search (FTS) features: 
http://world.episerver.com/Documentation/Items/Tech-Notes/EPiServer-Framework/EPiServer-Framework-61/EPiServer-Full-Text-Search-Service/

For developers, Find knocks FTS out cold. It's a breeze to setup, and a piece of cake to configure advanced, built-in features that you would have to custom-build in FTS. You'll easily google lots of inspiring blog posts on using Find - while googling FTS it seems you'll mainly find forum threads where devs struggle to get it working correctly ;-)

Thanks for the links!

The issue with Find is that it adds a monthly cost, which I don't know if it's acceptable but that's not my call to make. I'm just researching viable options to use for an intranet site that is in the planning stages.

Keep in mind with Find there's a (relatively) low monthly cost for lots of features out-of-the-box and minimum required development time. You'll also get support directly from EPiServer, minimizing the dependencies on third parties.

With FTS you'll require a lot of developer time setting it up and customizing features (well, unless you just want a barebones index and search results page). 

With other search vendors you'll likely have to pay a higher license fee and you'll be dependent on support from a third party.

Thanks again!

Find's features are awesome and I love to work with it but keep in mind that with Find you'll be adding a crucial integration point to your solution map. The hosted version has had some stability issues recently.

(I've got no experience of the on-premise version)