Skype is absolutely a disaster, but it's the only video chat solution I've seen that handles audio well at all (things like echo detection). The super-expensive fancy solutions like Cisco's offering are probably better, but I haven't tried. All the web-based tools seem to be different UIs on top of the same fundamental technology. I think Slack is nice and they generally seem to understand how to make software for humans, so I really hope they pull this off.