I was pissed that this was a PSVR exclusive for so long, so when it finally came to steam, I was excited but heard that it was only a couple hours long.
I got it during the Summer Sale and man... It's good. It's one of the most impressive visual quality VR games out there as it uses the assets from the Arkham games. That being said, it's crazy short. I found that it was MUCH shorter than that "couple hours" of gameplay. It takes around 45 mins to play through it, and that is REALLY taking your time to look at everything. It's got Riddler puzzles and stuff that can add to the 100% completion of it, which is fun, but not a couple of hours.
I think it's worth it for $15 just because you get the quality of Arkham games, in VR and the writing of it as well. Batman Arkham Asylum, City, and Knight were some of my favorite games of the last decade, so I thought it was worth $15. If you are on the fence, get it, I think you'll be pleasantly surprised. If you regret it, there is always the refund option.