Sonnet 4.5 did it for me. Cant imagine coding without it now, and if you look at my comments from three months ago, you'll see I'm eating crow now. I easily hit >10x productivity with Sonnet 4.5 and Opus. I use Opus for my industry C and math work and Sonnet 4.5 for my swiftui side project.

I think the gap between Sonnet 4.5 and Opus is pretty small, compared to the absolute chasm between like gpt-4.1, grok, etc. vs Sonnet.