Got a MacBook Air and also have a higher end MBP 16".
Since having an 2nd gen iPad Pro it was clear that Apple could convert their ARM CPUs into the generally first laptop and desktop capable ARM CPUs in the market. Still it is shocking to see how good the first round of machines actually are - minus some rough edges.
Sadly the form factor has not been updated. There are some rough edges (bugs) when driving external screens via HDMI. For example the machine has been hard crashing and rebooting while playing 4K/HDR movies in Youtube using Safari. It often forgets external screen configurations and the machine can wake up with strange display contents (like using the 4k-Screen only partially). My earlier Macbook 12" had similar problems driving external screens with the first year of OS software updates. My MBP 16" OTOH always had really excellent display support.
The MacBook Air can drive my external OLED screen with HDR support. What currently seems unclear to me if it will be possible to have 10bit color depth (billions of colors) on external screens. Apple is not showing information (-> I have not found any information about this) whether this is currently possible or planned for the future. The MBP 16" does 10bit color + HDR, though.
On the positive side, speed and battery life are excellent. I find the machine generally to be very responsive. There is no felt CPU speed/battery life compromise like with earlier MacBooks. After Apple had the bugs of the software for the MacBook 12" fixed (and it took them a year), that laptop was a very nice machine, but it was on the slow side with not much runtime on battery. The new MacBook Air is a different beast. It's also completely silent, just as the MacBook 12" was - no fan needed.
x86-64 support is much better than expected. Much much better. Software runs much better than I had experienced with earlier transitions (68k -> PPC, PPC -> Intel). Running iPad/iOS apps is great. The screen is actually quite good and I also found the sound with headphones to be great.
Next I'm looking forward to see more native software: VMWare, DXO Photolab, Microsoft Teams, ...
Right now I'm typing this using this configuration: MacBook Air in clamshell mode, LG 48" OLED screen, external keyboard/trackpad, stereo amplifier connected via Bluetooth, power&HDMI via Apple Digital AV Multiport Adapter.
Anyway, congrats to Apple. They've done some amazing work with the new machines.