Shameless race plug aside - having Horizons is awesome. Just landing and driving is a really cool experience ..
[video=youtube_share;yQivaH0EWfc]https://youtu.be/yQivaH0EWfc[/video]
.. there are amazing planetary bases to land at where you can trade and pick up missions just like the orbital stations (and also race - sorry, a lot of my videos are race videos) ..
[video=youtube_share;dvWl2bG5PI0]https://youtu.be/dvWl2bG5PI0[/video]
.. you can do things like base assaults ..
[video=youtube_share;npRVZKyvcws]https://youtu.be/npRVZKyvcws[/video]
.. or missions to destroy skimmers, scan surface beacons and retrieve stuff for search and rescue. Plus, as mentioned, you can land at the engineers bases (which are amazing locations in their own right) and get them to make improvements to many aspects of your ships (including jump range, speed, shield and wespon strength, etc, etc).
Or you can just go and do fun stuff with your buddies (or total strangers as in this case).
[video=youtube_share;cQRnMqEpU4Y]https://youtu.be/cQRnMqEpU4Y[/video]
P.S. apologies for all the videos but a picture is worth a thousands words, especially in this case. I guess if you feel a bit "meh" about it after watching then Horizons might not be for you but keep in mind that you get the entire Beyond series for free as well.