I am using Spacemacs since more than 6 months now and I am still very happy about the switch. A recent discovery is the layer imenu-list, which provides a persistent sidebar showing the outline of the current buffer.
So far I have been using SPC j i most of the time to jump around in the buffer. I have been missing a nice outline view sometimes though. It is especially helpful when I am working on a bit of source code which I am not too familiar with and don't yet know what i am looking for. If code is structured in a good way, the outline often tells a story about it.
Using imenu-list is as simple as adding it into your Spacemacs configuration in dotspacemacs-configuration-layers, it should work out of the box. Get started by SPC b i and find out all needed details in the readme on Github.