gdgt

kernco, I had the 2010 MBP, so know whereof you speak. I've only had my new Retina MBP for a few days and haven't watched much video on it yet, but in the course of setting it up and transferring data, I did work the processors hard enough to get the fans going for over an hour. As reported elsewhere, the sound is not so much quieter as different -- not as high pitched, so not as annoying, and not as directional. When I first heard it, I had the machine set up at our kitchen table. I actually thought I was hearing water running in the pipes under the floor. Five minutes later, I got out of my chair to see if we had a leak -- and only then did I realize it was my Mac! Hope that helps.

As to heat, again, it's early days, but I'd say it's more comparable to the heat from my 2011 MacBook Air Core i7, i.e., it can get hot but not burning hot. When used for web surfing, email and the like, it just gets a a bit warm. YMMV, especially, if you run a lot of video or game on it. I'd let other owners chime in on that score.

I've only had mine for a few days but I have played a few games on it. I had it on my desk while playing Trine and at first through it was raining, though I soon realized it is the fans. As someone with a gaming desktop a few feet away (with all sorts of fans in it) it was by no means annoying but certainly noticeable at times.

As for the heat... it's hot. Real hot. I can't personally share any comparisons with previous MBPs but while playing Civilization V the area on the upper half of the keyboard to the hinge was very hot.

I haven't yet bought a retina MBP so I don't have a definitive answer as to how hot they normally get. However, everyone in my family has one model or another of the normal MBP, and all of them can get quite hot, especially in the area right above the function keys. There are three reasons for this (these are true for both the normal and retina MBP models). First, the heat exhaust vents are right behind the screen hinge (you can see them if you look into the gap between the black screen hinge and the silver body), so this area gets exposed to the exhaust right as it leaves the computer, when its hottest. Second, the CPU and other main heat-emitting components are located directly below the upper half of the keyboard, further adding to the heat felt in this area. Thirdly, MBPs are made of aluminum. Metals are vastly better conductors of heat then plastic, and aluminum has some of the best thermal conductivity properties of all metals. This is important for keeping the Mac's internals cool since it means more of the total heat produced is passively lost through the case, which means the fans don't have to spin as fast as they otherwise would. The high thermal conductivity means that the case will also more rapidly transfer its heat to your skin when you touch it, and so it will feel quite hot (since most non-Mac laptops have plastic cases, the case will feel "cooler" since the plastic transfers less thermal energy to the skin per unit time than aluminum does). In short, unless you can cook eggs on your MBP while you watch a movie or something, the temperature is within the normal range.

As for fans, the normal MBPs have ones with symmetrical blades. Because of this, they each create sound at the same frequency, which increases the loudness of that sound and also gives your brain one sound to focus on. The retina MBPs asymmetrical blades each create sound at a slightly different frequency, so there isn't the same additive effect, and there also isn't one distinct "fan sound" for your brain to focus on.