I have had the i5/16/256 MBA for a month now, and having used it as my "main" computer for the past couple of weeks, it works just fine for my use.. which is mostly office work (no photo or video editing, no gaming). No "beachball", no overheating>shutdown .. nothing that seems broken .. including dead pixels. The only source of complaint is that the MBA does not have TB ports on the right side (charging purposes).
As background, my last personal Mac was a 2015 11 inch MBA with 8G of memory, but I also use a MBP 13 2018 with i7/16 for work.
<Burst Quickness> Comparing to the 2015 MBA, it is noticeably faster on things like "bounces before MS Office apps open" and the opening of other apps. Compared to the 2018 MBP, the "bounces" etc. do not have a noticeable difference to me, so it is not a concern and I quite like the burst responsiveness of the MBA, especially when compared to the 2015.
<Sustained process /Load speed> I don't doubt that doing things like handbrake conversions on 2020 MBA would take much more time than the 2018 or 2020 MBPs, but as many of the YouTube reviews mention, the MBAs can perform these tasks fine, ... they just take more time than the Pro laptops.. which is by design. So, for somebody that may or may not do FLAC to mp3 conversions of 50,000 songs once in a long while, it is not a big issue, because these things (for me) are not time sensitive and the process (and the fans that go loud due to the taxing processes) can run overnight. With something like a PPT to PDF conversion, it happens quickly enough that I feel the "extra" time it takes to do it is negligible. YMMV obviously.
## I actually use an old 2014? Mini as a music/file server in my house, so the conversions usually take place on the mini, at night, when nobody is listening to music or accessing files.
<Fans> I had one instance of the fan going loud in the middle of a Zoom call .. which self-subsided after a while for some reason. In hindsight, I think it was the one-drive(?) MS app making a connection that did this, as it was right after I did an install of my MS Office. Nothing really since then, even though I am being hyper vigilant about the fans spinning. This will obviously differ based on one's use patterns.
<Heat> I don't doubt that the MBP has better thermal design, and that goes to the sustained performance difference. However, where I differ from many in experience is, I think the MBP 2018 runs warmer on the lap than the MBA 2020 does. I am guessing that this is due to the better thermal design of 4TB MBPs, where the 4TB MBPs have slits on the side of the bottom case for ventilation purposes and heat from the vents (which, again, contribute to a better performance of the machine) make the MBPs feel warmer. Again, this will differ based on use patterns, but for me personally, doing the exact same tasks on MBP and MBA, I thought the bottom case of the MBA ran cooler than the MBP 2018.
I will likely move my "main" personal home computer back to a Surface Book 2, due to the larger screen, having the MBA as a mobile computer, but I would not have a problem using the MBA as my main going forward either.