The vote is clearly in, and the majority is siding with Apple. I haven't changed my position, though, and the more you write in this thread, the more convinced I am that you don't know what you're talking about. The technical reasons are not strong; SSE2 is primarily for floating point ops and SIMD vectorized ops. Most user code does not use floating point, and it's hard for compilers to extract latent parallelism to produce vectorized code.

However, if you put the technical reasons aside, and only focus on the business reasons for making a choice here, it's clear to me that the best way to go is to fall in line with the existing precedents for the platform. That way maximizes your business upside. There is no business reason for wanting 16-byte alignment, only business reasons for not wanting it.

The technical case would need to outweigh the business case in order for it to win. But I don't see the technical case as being that strong. Floating point code is rare. Outside of scalable vector-oriented UI libraries and ___domain-specific number crunching, it's hardly ever used. Many architectures survived for decades with only optional support for floating point, in a coprocessor. Many embedded architectures still use emulated FP, if it's needed at all.

And I really meant it about shockingly naive back there. It tells me everything I need to know about what you know about commercial compilers: that you think of them in the academic sense of being the bit that turns text into code. There's more to it than that in the real world.