Good question! I like the 1 minute auction format and I appreciate, as a buyer, how shipping is calculated (automatically by the app). Some of the sellers I find to be very entertaining and there's a budding community there. However you have to trust the grading of the seller since there's no time and no high quality photos/scans/images that you get to look at. It's also an environment that loves to hype things up while inviting you into a million giveaways and mystery boxes. I find it as an enjoyable way to kill time while noticing what some speculators are up to. I don't follow most spec stuff elsewhere so it gives me a bit more insight into why some random books I'm looking for jump in price. If you like instagram live sales and have a few sellers you trust, then I feel like you'd be into the app. I'm fine buying (super) small dollar books on the app and would consider buying a slab from a dealer I already trusted. But I'll keep my key buying restricted to only on the boards, at my lcs, or at conventions where I can (sometimes) review the book for a longer period of time.