Is it worth switching to CSP if I'm already happy with direct Microsoft billing?

If you're genuinely getting the support, flexibility, and pricing you need directly from Microsoft, there's no inherent requirement to switch — CSP is one option among several valid ways to purchase Microsoft cloud services, not a universal upgrade. The honest answer is that it depends on whether you're missing something (consolidated billing, more responsive support, cost optimization help) that a CSP partner relationship would actually add for your specific situation, which is worth evaluating concretely rather than assuming either path is automatically better.