I've certainly learned areas of history that I had not been versed in before. The first two seasons focus on the failed rebellion of Scotland's Bonnie Prince Charlie, an era that I only knew a song about before. While the characters meet a few historically famous people, I'm particularly intrigued with how the show (and the novels) show the day-to-day life of regular people.
The show deviates from the books, yet stays remarkably faithful to them as well, as the best adaptations do. In some cases the show changes parts that were not quite believable in the books. Oddly, it also occasionally makes less believable changes as well.
The show is well done, with good writing, great acting, and fantastic sets and costumes. It been a good show to watch as a couple. I don't think that I'd want to see it around my kids ... or my parents.