Boy, what an involved process. So many screws. So many ribbon connectors. Ended up being a whole afternoon operation.
I followed video of a guy taking one apart on youtube (can't find out which one) but I did the same mistake he did before I got to that part and cracked the ribbon cable connector for the blu-ray drive - it flips up. It still works so I guess it makes enough of a connection but it may be on borrowed time. I also temporarily lost the memory-card cover spring although I found it the next day (but didn't want to open it all up again).
I got it down to the point of taking the fan out to clean it - it has some very stuck-on dust which I wiped off, but apart from that most of the dust was outside of the main cooling thoroughfare and so was pretty irrelevent. After getting it all back together it didn't really make any difference. I had mine sitting on a frame I made up because until i blew up my amp it was sitting above that and both needed the ventilation - that probably reduced the dust getting into the insides.
In hindsight I should've just left it alone!
I only got about 2/3 the way through taking it apart too.
However I guess it was interesting to see the thing for myself. That fan motor is a total monster and the heatsink is gigantic - most of the whole base area. It must've cost a fortune to make and to assemble. With all those separate parts and shielding pieces to put together the initial production must have also been hard to test and very failure prone increasing costs.
Looking at the video tear-down and pictures of the PS4 motherboard the thing that immediately struck me is how simple it is: i'm not a hardware engineer but I can imagine that simple means cheaper to make. I wouldn't be surprised if the PS4 is already cheaper to make than the even the current PS3 on a per-unit basis - and if not it is something that will become much cheaper much faster. It's probably a lot cheaper to make than the xbone too, and again something that will become cheaper at a faster rate. Dunno where all those passive components went.