No clue about GPU stuff, but I'm kind of thinking of an analogy with video encoders. Like there's hardware specific for encoding functions these days on some chips, I don't know how much space/transistors they take up, but I'm pretty sure they're more efficient at the task than general compute processors like regular CPUs or in this particular case, programmable shaders.
Perhaps they could make some stripped down shader units primarily for whatever effects (tesselation, lighting, blah blah), rather than necessarily making magic new hardware. It'd kind of fit in with the argument that if they had something special it'd already be in use in their other GPUs, since this would be sort of cutting down something existing to make specialized hardware rather than creating something new from scratch, whereas on higher end hardware they could just throw on more standard general use hardware.
But that's all just crazy speculation.
I personally hated GX, so I'd be very happy if it were very different. I mean, the gameplay started great, but the balancing was WAY off, the game went from fun to frustrating very quickly.
I liked Sunshine, but I don't love it. It was too frustrating at times for me to really enjoy it. It took the fun of it. I never even finished the game.
Obviously the GameCube was too hardcore for you guys.
I loved them both myself, although I will say for F-Zero what helped a lot was my custom vehicle, I think the combo was called "Super Horse". I guess the key is just trying out the different vehicles and/or building your own to get one that really suits you. The story mode (where I think you had to use Captain Falcon's vehicle) gave me a shitload more trouble. As for Sunshine I liked the general feel of the whole thing, and just the prevalence of platforming around on stuff in most areas. I could never get into 64 cause (at least early on) everything is so spread out that it felt like there was more running around than platforming.
I thought both were good difficulty wise, hard enough that you're not just going to walk through it, but not impossible as long as you work at it. Even if you lost a lot you could generally see progression and have hope that you'll eventually make it. Unless you give up easily.