I've talked to many people on IRC who have told me windows 95 received about as much hate as 8 is right now.
Also 98
Also XP.
Also vista
In fact whenever there was a change, there were people threatening to switch to linux.
The only difference between the hate on 98 and the hate today, is that social media has significantly evolved and adoption of a social media network is near universal. Those people who complain about nothing, can now be heard far and wide, and since hating microsoft products is the bee's knees, no one actually needed to try 8 to know they 'hate' it.
To further compound the issue, most of the 'hate' started with the 8 Developer Preview, which was _not meant for consumer use_. Some bloggers loaded it up on their computers, misunderstood how it worked, misunderstood that it was a pre-alpha, and forever tainted the image of all future releases.
Here are the facts.
Windows 8.0 and 8.1 are lighter and faster than 7 and Vista (although not lighter or as fast as XP, but remember XP is ancient and is rather bare bones by today's standards). All of the improvements under the hood that went into 8 are the exact reason why it is objectively better than 7- 8 features an updated, overhauled, improved NT kernel. 8 is pretty vastly different from 7 even without the touch friendly tweaks.
If someone installed 8 and found it to be slower than 7, there are a number of reasons that could be, but it comes down to an end user problem.
1) Unfortunately, 8 won't run perfectly on all hardware (that of course will improve over time). In my experiences, this is actually *incredibly rare*, but one person tweets about how slow it is and ignorance spreads... Since 8 is lighter than 7, it's definitely a better bet that 8 will run faster than 7 on older hardware though.
2) Drivers. Most Vista and 7 drivers will work fine on 8, but not all. There are a few pieces of hardware in driver limbo- rarely, a 7 driver won't work well under 8, and the manufacturer will never update it to work with 8 because it's old hardware. This isn't exclusive to 8- I have a PC that won't run 7 well because all the XP drivers just don't work well with 7. Not 7's fault. Not 8's fault.
3) If you buy a PC with 8 on it, you're not getting vanilla 8 more than likely. You're getting the **** encrusted OEM branded windows install. So yes, a fresh install of 7 will definitely be faster than that- but you can see why users in this scenario do not have the ability to make a fair comparison. If they had done a fresh install of 8 instead of 7, they would have found the fresh install of 8 to be faster than whatever tainted version of 8 was preloaded onto the PC they bought.
OP asked how this compares to other OSs? XP will always have a place in my heart, but it's dead now. I did not use 7 for a very long time actually, because I was very unhappy with how bloated 7 felt. 8 has all the benefits of 7 and more, with a lot of the bloat reduced.
HOWEVER, 8 & 7 require at least 16GB of space, and I have several devices with 16GB SSDs. I installed 8 momentarily on one, it worked, but with 500MB of space free... I opted to install linux on those devices. The distros of linux I use take up maybe 400MB of space. So if you're using devices with less than 30GB, space is going to be a concern, and that's a valid reason to stay away from 8 AND 7 (7 also requires at least 16GB). I've seen a lot of complaints that 8 takes up too much disk space... completely ignoring the fact that 7 was no better.
What with all hardware being made with 8 in mind, it won't be long before 7 has 'driver limbo', where most drivers either won't work with 7 or won't work as well on 7 as they do on 8. I predict the next iteration of windows will add some polish to 8's interface with not much changed under the hood, and people will try it again and think "wow how much better than 8 this is!"... not realizing it's the same OS with a slightly better skin.
Another thing- many judge things by visuals, and to each his own, but most of the voices "hating".. anything, not just 8, are 12 year old kids and manchildren- these people decide something is bad over the most insignificant detail. Having already made up their minds, they then do the bare amount of research, only looking for negatives, and well, confirmation bias is a powerful thing.