I agree. I like the hashtaggy version above because it's simpler, has the hashtag implication, and has the love of Slack the company I've built up over the years.
One thing that's bugging me a little is the Slack logo is starting to be associated in my mind with Slack the product (different from the company) that provides no respite, an inability to focus on something hard until Slack quits popping in the evening. I once interviewed an engineer from Netflix for a position at Cake and he said some significant number of people at Netflix had determined Slack was a productivity killer and had opted out. I was surprised at the time but I'm not so surprised now. It's as if everyone decided to stop emailing and start texting when Slack burst on the scene.
Anyway, now when I see the Slack logo I tense up a little bit and think I'd better scroll back and see how much I missed when I was meeting someone in San Francisco for Cake.