I'm using GitBucket and couldn't be happier ... We've got a GitLab installation at work, but for my personal projects I didn't want a front-end that relied on RoR (since I'm not proficient). GitBucket was reskinned with the modern GitHub look for version 2.0 and is written in Scala and run on a JVM (both of which I'm fluent in).

I should also note that I was a happy Gitolite user until it was obvious that having a web UI would speed adoption ... both GitLab and GitBucket provide the user and group mechanisms you expect.