Well I am basing my opinion on this
AnandTech | First Look: The $799 Microsoft Surface Pro 3 with Core i3
Also I use a core i3 laptop at work and compared to my surface pro it crawls. Maybe its the 4200 rpm hdd. Ok maybe calling it a terrible chip was too extreme, but I did want to highlight the performance difference to potential buyers so they won't be disappointed after getting one!
That said you are right. A core i3 is good enough for basic computing.
my i5 laptop with the old HDD 4200rpm is also dead slow.. I just change it to a 40GB SSD, its like night and day... so the bottleneck isn't the cpu but the HDD/SSD then.. So your i3 laptop could also be bottlenecked by your HDD..
If you check out the anandtech site, look at the DOTA2 chart, this is the only real world base program (running hard on the cpu n gpu), the rest above are just benchmark programs
notice how i3 can out perform i5, its not i3 is better than i5, but its i5 is over heating and it pushes the cpu and gpu clock speed down.. down so much as its on par or its lower than i3
Anyway, when I had my sp1, I also faces all these heat issues and I really run the sp1 at its minimum clock speed (i5 at 798MHz) most of the time, the sp1 has a better cooling subsystem(2 fans), the i5 3rd gen is rated 17Watts, but still its hot.. so a 15Watts i5 on a weaker cooling subsystem(1 fan) sp3, can only think it will get hotter if running max, but if i can't run max performance, and always try to down clock it and idle, why get a i5/i7? isn't i3 just a down clock i5? (i7 is a little different, it has a diff cpu n gpu than i3/i5)
if there was a 4/GB 128GB i3 or a 8GB/256GB i3, i will still choose i3 over i5, just because the thermal design of the sp3 is limiting i5. I am sure broadwell will be a better fit and then i5/i7 will be a much better choice...
Well, just my own view point.. everyone is different..