For instance, I reported a DoS bug that can cripple freemium communities and they basically told me "oh well". For obvious reasons I'm not going to go into details here, but I've got a script I can point at a slack freemium slack community to wipe out a lot of it's functionality that I built as a proof of concept and they just don't seem to care.

There are also huge issues with moderation and harassment on the freemium Slack. Since there is no way to block or ignore a user it gives trolls an insane amount of power (and before someone tells me that you can mute notifications from a person, I'll mention that all the troll needs to do is create a new chat room, force invite the person to it, and continue trolling to bypass it).

Personally I find it really frustrating that slack has kind of destroyed a bunch of IRC communities, but is refusing to build the tools needed to manage these replacements. As more and more freemium communities are figuring this out and migrating I imagine the people pushing Slack because it's what they are familiar with is going to drop.