And what is the reason to keep the power limit so low? Higher power brings with it higher costs (cooling, packaging, bigger psu), but also much higher performance, and performance was the problem with 3rd party software. I'm not saying they have to launch a 150-200W system, but 100 W is reasonable. There are 100W fanless,single slot card out there. A tweaked/revised RV740 may hit 50W (at 40nm, because i don't think they will use 28nm) and the entire system could fit into 100 W.
But it's true that the devkit doesn't seem power hungry at all. PSU may even be internal
It's a question about priorities, really.
You can either start with a performance target, end up with a (high) power spec, and then work your ass off trying to squeeze that into something living room acceptable. Or you can start out with a power/form factor spec, and then try to make it as performant as possible.
(By the way, I used to own the highest end passive card available - the HD5750. It drew just under 75 W, and was in NO WAY a single slot product. Now I see that Gigabyte has recently launched a passive HD5770. I don't know if they have now been able to drop drive voltages a bit so they get down to 75W as well, but their cooler is even bigger)
Longer and maybe redundant discussion:
You made a good starting list yourself of why high power is undesirable. I would add that high power draw is a negative in and of itself, mostly from an ideological point of view, but also cost and heat generation. The biggest issue for me is noise, I would never have bought either of Sonys or MSs offerings at launch due to noise, even though the Sony was better. Even now I didn't buy a PS3 slim as a BluRay player due to player noise being unacceptable. The smaller physical dimensions made possible by lower power draw is also a positive which is very important to some. Not to mention that heat increases the likelihood of heat related failures and RMA costs throughout the distribution chain.
Cost is greater throughout - as you point out the cooling apparatus needs to be more sophisticated, the packaging needs to be bigger to accommodate it, the PSU is larger and heavier, all of which is costlier in and of itself, but also in shipping/stock keeping. And in the real world, significantly higher heat is likely produced by a larger piece of silicon, again something which raises costs.
The big question is how relevant all of the above is to the end consumer. I'll submit that the clientele here at B3D is extremely insensitive to the drawbacks of high power draw compared to the public at large.
That said, if you're doing a mains powered stationary device, going very low in
active power draw may be overly restrictive. There are going to be a bunch of things drawing active power in the system anyway so having the GPU draw very little doesn't actually bring a tremendous benefit for the system as a whole, personally I'd prefer a power draw of 30-50W and good, near-silent, cooling along with very low idle power draw.
