For me it replaced a free calendar publishing plugin with limited functionality. It separates your writing activities from the publishing activities. I haven't use the social publishing features, I use Missinglettr for that, so I can't say much about those features.

I really do like the calendar. I only used the manual scheduling option. It gives you a good perspective on your publishing activities. After you have saved your post it appears in the calendar tab and you can move it around on the calendar easily.

When you move the post into the past it is immediately published, no need to press any buttons! When you move it to the future it is automatically scheduled on 12.00 that day. So it's quite easy to adapt your publishing schedule after you have finished writing multiple posts, without going into every post separately. You can also republish or unpublish WordPress posts at any time you want, which isn't possible in Wordpress, as far as I know.

The plugin even is able to prevent "Missed Schedule"-errors, due to wp-cron errors. I did not experience those yet, but I can image that it makes publishing more reliable.

Support is responsive. I had a licensing bug issue because of the rebranding to SchedulePress. The ticket was answered quickly and I could continue working with SchedulePress. A few weeks later the bug was fixed and I was neatly informed. Great developer!