One was the first gen Alienware M17 with two GTX 270M GPUs (yes two) and an onboard nvidia GPU whose specific model I can't remember. That one suffered from stutters and audio crackling, etc. It was sort of fixed by disabling SLI and the onboard GPU and sticking to a specific driver that was modded, the driver was by someone on the notebookcheck forums IIRC. Later on I think it got somewhat patched with a bios update that let you use SLI without the stutters, but I think the laptop reached EOL without it being fully fixed.
The second was an ROG ASUS laptop with a GTX 460m (I can't recall the laptop model). Pretty much the same story as the OP but I didn't have the knowhow to go deep into the ACPI code. The only change from the story is that latencymon kept attributing the latency spikes to multiple dlls, sometimes it was some wifi driver, other times it was an nvidia one. I don't remember the full fix for that one, but it involved me changing the wifi card and disabling the dGPU (not the onboard one) when I was not gaming so I could watch videos and such without it crackling. Funnily enough it didn't crackle much when actually playing games (it still happened, just very rarely).
I stopped buying gaming laptops after that. Seeing this story makes me think things haven't changed one bit.