Building a large project feels like building a house of cards. I often run into small but infuriating UX issues inside their app. One example of this is uploading artboards from Sketch using the InVision Craft plugin. Uploading a new artboard that has the same name as a previously uploaded artboard overwrites the original without asking or telling you what happened. I spent way to long trying to figure out why one of my artboards wasn't uploading, and then it took me even longer to figure out where it ended up once I realized the problem. When you have hundreds of screens in a project every upload from Craft starts to feel scary.
These little interactions are all over the app and the amount of frustration they cause becomes exponential over time, like a repetitive strain injury.
I've been an InVision user for a long time and it seems to me that the core features have not improved, but have actually degraded over time. I assume because they put all their resources into Studio.
I hope they use some of this money to improve their core offering. Sketch users aren't going away and I think it would be wise to try and keep as many of them as possible using InVision.