We ended up adding access group support to SA5’s user info lib for a client project.
Details are in the SA5 docs below.
If you need a much faster and more powerful solution, we have a new approach that gets the entire user info record instantly and allows you to personalize your site based on the current user’s access groups, custom user fields, etc. We use it most often when a client needs high-performance personalization features, “partially” gated content like an article preview, or tighter security controls like instant lock-outs. Drop me a message if you need to talk about a custom build with features like that.