SAO: Lost Song is basically just a pretty game for fans of SAO to enjoy consisting of Kirito n' Friends clearing Svart Alfheim; no overlying grand storyline. The fanservice between Kirito and the heroines is much more toned down than the epic Hollow Fragment where everyone gets a kiss-on-the-cheek CG, but they still get their moments.
You get four very large open-worldish but eerily barren and empty islands to roam around and fly in to conquer four to six same-looking dungeons before you get to battle the Area Boss to move onto the next island
Combat is pretty much mindless hack n' slash, though some bosses can hurt so you'll have to be a bit cautious around those.
Overall Lost Song's event scenes are severely lacking compared to Hollow Fragment's; most of the scenes I've read through so far are just the characters doing whatever's in the moment, and it's really, really "meh" stuff.
It's still a pretty game though, yes visuals matter, and you can't discredit the awesomeness of being able to fly around in a large landscape, or getting to sideline Kirito and having any of the SAO heroines as your lead party member instead.
At this point though I'm only making the grind for
Spoilers, I guess?