
Oh boy, this may be device-ive.
I only have experience with the HeroQuest companion app, and I don’t prefer it. I feel like it takes away from the minis and the board. I find that we often shortcut/neglect the physical board. Then we’re playing catchup to the app. I’d much rather look at minis on a board and live in that world than look at essentially a videogame.
But that means you need a dedicated Zargon, which not everyone can manage. But, in my opinion, going app-free is a much better experience. Luckily/unfortunately(?) there are no Warhammer Quest apps that compliment the board games.

Counterpoint, though I haven’t played the game myself, is Betrayal at House on the Hill. I hear this game (and app) are a TON of fun. I’ve read that the app is good spooky fun and can really freak you out sometimes. I’m intrigued, but also, I have plenty of games.
App longevity is also an issue. How long will it be supported? Are you paying for additional content that you’ll lose once the app is deprecated? This has already happened with the Silver Tower app. There were some exclusive heroes and additional content that was only available in-app, but gone now.
What are your thoughts? I’m curious if there are good experiences out there.