I tried both of the i5/i7 256 models. I worked those machines hard. I have pretty hard hitting programs open and running at the same time, not to mention browsers and browser tabs. Did it get hot? Absolutely. However, they did not shut down and they only time I've heard the fan is during firmware and Windows updates.
The i5 performed well, but I did notice that it bogged down for me a bit towards the end of the day. I haven't had any "issues" with the i7. I know that there are reports that there is not really a significant performance difference to justify the price increase, but I think that I noticed an increase and decided to stay with the i7.
"Despite having the same TDP (Thermal Design Power) rating of 15W, The i7-4650U processor in the SP3 gets noticeably hotter than the i5-4300U version. During our testing, all of the testers said the i7 version got uncomfortably hot at times. Especially in the upper right corner of the screen."
I's take this article with a grain of salt though as it makes no reference to so-called throttling behaviour of CPU's. In the SP3's you see that depending on the heat that is generated, the CPUs tend to start throttling down their operating frequencies as prevention measure against overheating. Since the i7 generates more heat, it also throttles a bit more. So depending on your usage pattern, your experience may actually differ.
In my case for instance, I predominantly run virtual machines. Sustained CPU performance and turbo boost therefore is not as important as for instance with graphics work where rendering and filtering may put a CPU through its paces a lot more. So between an i5 and an i7, I found the i7 to be a *lot* faster when using it for my particular purposes.
For serious gaming and graphics work however you may actually find that the larger cache and higher frequencies of the i7 are somewhat compensated by a higher degree of throttling.
For me the choice is a nobrainer, it's the i7 all the way. For others it might simply be a different choice
If I hadn't seen the difference between an i5 and i7 with my own eyes side by side, I would have got the i5. Mind you this is the SP2 4200U versus the SP3 i7 but the difference in performance was HUGE.
This was specifically on MYOB but also on Norton scans. Web pages also fired up noticeably quicker.
It does depend on your uses too. In my case, I am out using MYOB on customer sites, multiple times every day so the performance of MYOB is important to me. In fact if it wasn't for this issue (MYOB is slow), I might have been satisfied with the i5.
Numbers and dead men tell no lies ... ... neither do they tell the truth. If nobody's been recorded saying that before remember where you heard it first
Cost per unit of measure, be it dollars per gigabyte or apparent performance, is one way of expressing comparative value however it may not reflect the measure that's most important to your situation.
Perceived performance, heat, value, etc. includes intangibles or unmeasured characteristics that affects how we sense the individual or combined attributes as a whole. Reports seen above in this thread reflect greater perceived characteristics than the straight numbers would indicate.
Possible explanations for those discrepancies.
1. The benchmarked performances are not fully reflective of the real world.
2. With higher overall performance a smaller percentage difference is more noticeable.
The second point is quite significant as 10% of 100 is 10 points while 10% of 1000 is 100 points. A 10 point increase may not be noticeable while a 100 point increase may be very noticeable. At these performance levels percentage may not be the best measure to derive real value.
I also have an i7 and love it. I've never had any overheating issues. Usually it's cool as a cucumber when running standard "stuff" even full photoshop CC, at most it will come on at low level very briefly. It is a PC after all, you can't expect the fan not to run.
Interestingly for me, other than major taxing tasks like rendering high resolution photos the fan only comes on full blast when doing a major download, or when I'm playing Age of Empires - Castle Siege... which is a windows store game i'm currently addicted to. I have no idea why that makes the fan blow.. it really eats battery too and it gets quite warm.. but never actually overheats/shuts down. It also makes my phone very warm and kills the battery there too when I play it on my Windows phone... so not Surface specific!!
Other than that which is an app issue rather than Surface issue, I bloody love my SP3 (to coin a British phrase!) Best computing device I've ever owned.