I'm using the free self-hosted version of Metabase and it's been great. My only real issue is the lack of custom stylesheet support.
Being able to inject a simple CSS file (without modifying source) would go a long way toward matching internal branding and making dashboards feel more natural for my end users. I understand something similar exists in paid tiers, but for small teams self-hosting on a tight budget, even a basic styling hook would be a massive improvement.