Switching to Opus is an eye-opening experience. You hit limits often, and need to get creative to avoid burning through limits, but the difference is seriously impressive. You'll waste a lot less time with dead ends and bad code.

The issue (with Sonnet, I'm not using Opus), is not always that the code is bad per se, but merely that it doesn't solve the problem in the way I expected.

I have two problems with that. Firstly, I want my code to be written a particular way, so if it's doing something out of left field then I have to reject it on stylistic grounds. Secondly, if its solution is too far from my expectation, I have to put more work into review to check that its solution is actually correct.

So I give it a "where, what, how" prompt. For example, "In file X add feature Y by writing a function with signature f(x: t), and changing Z to do W..."

It's very good at following directions, if you give it the how hints to narrow the solution space.