I suspect it must depend on how one manages their codebase - wrt to docs, ADRs, and general guardrails.

For me it is not great for design work - Fable is way better, and 4.8 was conservative and thus better (Opus 5 seems to jump to conclusions far more eagerly). But for overnight builds, where I give it 8hrs worth of work on LLDs created by Fable - its great. Where Opus 4.8 would often lose the plot and stop for questions clearly answered in the LLD - Opus 5 does manage to complete. Since it launched, I don't remember it ever disappointing me with builds. But designs? Boy, is this thing explosively stupid sometimes.

Opus 5 loves to stop working "for safety reasons" and shuts down the session! I avoid it at all costs now. Opus 4.8 has been my default as well.