Oh boy, where do I start?
First up, let's begin by pointing out that I know at least one of their integrations actually violated the licence of the platform it was for - the SMF 1.1.x integration straight up violated the SMF licence because SMF prior to 2.0 was not truly open source and they were shipping copies of SMF files, strictly against the licence. I don't know if they just quietly discontinued the 1.1.x version or if SMF had to "remind them" about it with lawyers but it couldn't happen to a nicer bunch of people.
Then there's the whole premise of their app. I get the convenience factor, especially when it first came around and it wasn't viable to do push notifications to a phone without a dedicated app (because browser notifications didn't exist, and they're only just coming to iPhone later this year, apparently). But it did what I've been telling people about for years whenever the 'but we want an app' argument comes up: it means your site is reduced to the same thing everyone else's is, and none of your customisations mean a thing. If you happen to be in a world where your site is in any way interesting for features beyond 'just the forum', none of that is exposed. Nada. Which is a serious turn-off for a surprising number of sites. You get the lowest-common-denominator feature set (which is also why none of the forum vendors are in any hurry to build an app because for it to ever make sense you have to interoperate, and none of them are going to reduce their own offering)
Then there's the fact that when they did offer a product in this lowest-common-denominator format, it was frequently buggy, demonstrably disregarded security settings (e.g. SMF sites set to registration disabled or admin-only approval would find new members registered and able to post by way of the app)
Then of course you have their little directory which is just crying for 'I don't really like this forum but for minimal effort I can find others that might be better'.
But I will absolutely give you that their virus like take-over of various of the forum hosts (not just Zetaboards and InvisionFree but also plenty of smaller ones that just slid by)... was the worst. It's the sort of thing Internet Brands (the vB owner) or VerticalScope (owners of Threadloom and TAZ) would do, except somehow scummier, like they were actually pretending it was for the forums' benefit.
Just ew. THOU SHALT NEVER DARKEN MY DOOR, HEATHEN APPLICATION. BEGONE WITH YOU.