We currently have a team of 14 people based in the US, Canada, Australia and the UK. We used to have a main office in San Francisco, but now that our team is not mainly concentrated in the Bay Area anymore, we are now truly remote only.
Slack works well for us in terms of asynchronous communication. When I start work in the morning, I can quickly reply to questions people in other timezones left me overnight. For group video calls we still use the old Google Hangouts, as the new Google Hangouts Meet is very much a downgrade at the moment. For one-on-one meetings Slack's video call feature works quite well – I especially like the feature to draw on the other person's screen during screen sharing.
We use Trello for tracking tasks and prioritizing work, falling back to Google Docs if something needs more than a card to describe it. GitHub has been invaluable for remote collaboration, which is why I consider their acquisition by Microsoft earlier this week to be a cause for concern.
Having a fast, reliable internet connection is essential for remote-only. A good microphone helps too. And having a separate room that you use for your office helps to separate work and family life.
We try to get together at least twice a year in the same location (usually Santa Cruz), as it's true that remote work is not a substitute for human interaction. These offsites are usually reserved for prioritising tasks and overall company strategy. I also try to work from a co-working space in town at least once a week, to stave off loneliness and interact with people working on other software-related projects.
From my experience working remote for almost three years now, the benefits outweigh the disadvantages by far. If you have the opportunity to work for a remote-only company, or if you can transition your existing organisation to a remote-only one, I would highly recommend it.