I've been using gstack for the last few days, and will probably keep it in my skill toolkit. There's a lot of things I like. It maps closely to skills I've made for myself.
First, I appreciate how he implemented auto-update. Not sure if that pattern is original, but I've been solving it in a different-but-worse way for a similar project. NOT a fan of how it's being used to present articles on Garry's List. I like the site, but that's a totally different lane.
The skills are great for upleveling plans. Claude in particular has a way of generating plans with huge blind spots. I've learned to pay close attention to plans to avoid getting burned, and the plan skills do a fair job at helping catch gaps so I don't have to ralph-wiggum later. I don't find the CEO skill terribly effective, but I do like the role it plays at finding delighters for features. This is also where I think my original prompting tends to be strong, which could be why it doesn't appear to have a huge impact like the other skills.
I think the design skills are great and I like the direction they're going. DESIGN.md needs to become a standard practice. I think it's done a great job at helping with design consistency and building UIs that don't feel like slop. This general approach will probably challenge lots of design-focused coding tools.
The approach to using the browser is superior to Claude's built-in extension in pretty much every way (except cookie management). It's worth it for that alone.
For people who don't understand this...think of each skill like a phase of the SDLC. The actual content, over time, will probably become bespoke to how your team builds software, but the steps themselves are all pretty much the same. All of this is still early days, so YMMV using these specific skills, but I like the philosophy.