That's an interesting question. I've been meaning to write something about it for ages. Here's a brief:

People, vision and ways of working. With time, I've developed my values and principles that makes me practically unemployable if I don't turn a blind eye to some of them. Alternatively, I could start my own company.

    * Small, empowered, and trully cross-functional team;
    * Highly collaborative in ensebles;
    * Unified flow with limited WIP;
    * No middle-management;
    * Little-to-no hierarchy;
    * No titles or levels;
    * Team-set salaries;
    * Organic team growth;
    * Test-driven;
    * Trunk-based;
    * Continuous delivery;
    * No perverse incentives;
    * …

Like XP, they complement each other. So, in order to actually reap the benefits of a practice, other practices ought to be adopted too. Many of the cargo-culted practices and problems fade away when doing things fundamentally different. And very few places challenge the status quo (especially when it comes to management). Forming a (real) team is very hard, and very fragile. Like trust, which I didn't mention above, as I believe it to be a natural consequence of building such an environment.

Needless to say that it is pretty much impossible to find a place like this. Although, with some compromises on my values and principles, I consider the current company I'm working with way above average; granted, I helped shape the culture, which seems to be diluting/changing now as the compromised values are missed. The company is trending towards mediocrity in that sense.