I was doing a "spring" cleanup on my MBP Mid-2007 and from inside, there was not much dust, just little as it had a new mainboard replacement in 2011. I decided to do the heatsink paste as mine was running quite hot.
After cleaning the heatsinks and then do the 'heatsink' tint as per instruction by Arctic Silver but instead using lint-free cloth to remove excessive AS 5 from CPU heatsink, I used the plastic card and scraped the excessive off and there was remaining paste was left in the middle, which means the CPU heatsink has slight 'dent' on it. No matter how hard or how many times or directions I tried to remove it, the paste just stays in the centre. I did not have this 'dent' on GPU and chipset heatsinks though. Could it have caused by years of excessive heat from CPU?
I have been using Macbook Pro 2007 for over 6 years now and it is still my first Mac computer. I had repaired and serviced computers for years so I do have some experiences. Here is my few thoughts on MBP:
Macbook Pro body is made of aluminum and we all know already that aluminum is a great heat conductor. However, when the MBP is running hot, aluminum is more uncomfortable to touch/feel than plastic one and that's one of the main drawbacks of using aluminmum laptop, be it Mac or PC. When it's hot, it feels hot and bothered! At times, it felt like handling or typing on a hot water bottle!
If aluminum is a great heat conductor, the heat from CPU would have dissipated easily through the heatsinks in contact with aluminmum body but why were we seeing such a high temperature figures in comparision with similar specced but cooler plastic-body laptops? Even plastic-body laptops have just one fan!
I believe it is more of insufficient cooling design, mainly a lack of inlet vents and when I was taking apart my MBP, there is no air inlets for the fans to draw external air in to cool the heatsink so it would have the draw the air from somewhere in its own enclosure and enclosure itself being aluminum!! This is exactly what happens when you block the cooling inlet vent and as a result of this, PC laptop heats up easily but all I have to do is to clear the inlet vent. So would drilling some holes on Macbook Pro help?
Every time a new generation of intel CPUs come out with smaller die and I thought 'Great, Macbook Pro would runs cooler with this one' but then, Apple has moved their own goalposts...by making their Macbook Pro and iMac to be even more thinner!
FYI, I repaired 2009 or 2010 iMac and it was choked full of dusts which builds up the heat in no time. I had to clean it twice for my friends over the course of few years and it's not good considering its age. Overheating in an enclosure with poor ventilation can cause all kind of problems. Their DVD drive cable failed and a failed harddrive probably due to overheating. While taking it apart, I noticed that there is a small air inlet, which is a ram slot cover on the bottom of iMac and if the inlet is small then it doesn't take long to be clogged up with dusts again...and also on outlet vent on the back centre of iMac, again it is small and clogged up with dusts as well.
Last year, Apple comes out with a much thinner and newly designed iMac (2012) and a PC Pro magazine were commenting on it about it reaching 100 C easily -
http://www.pcpro.co.uk/reviews/desktops/378763/apple-imac-21-5in/2 and that's not good considering it is a brand new and all it needs a few speck of dusts to overheat easily! Google it and you will see some people complaining about how hot their iMac is, even in sleeping mode!
To sum it up, I do not like the direction the Apple is heading, especially them being obessed with trying to make their portable more thinner. After seeing some cooling design issues and poor heatsink machining as pointed out by Doward, it is hard to image how I would spend ££££ on MBP running hotter than normally is for plastic body laptops. Aluminum body should put them a cooling advantage over plastic one but so far, it seems they haven't taken advantage of that.
I am not bothered at all with how thick my 2007 MBP is as long as it fits in my messenger bag but why the need to go ahead to make them more thinner and coupled them with powerful CPUs which might be throttled back?
Laptop PC is looking more appealing for a few reasons - They are cheap, cheeful and runs cooler.