I have MBA 2018 for about two months now and I would like to share my impressions.
What I definitely love about it, is the smaller footprint. This notebook feels just right in terms of size to me and is also pretty light. The screen is really good too, despite people complaining about the brightness. Think how often you use maximum brightness on your MacBook Pro. You probably never do, or almost never do. The screen in MBA 2018 is definitely bright enough for me. The keyboard is really comfortable to type. Sound quality is the best I've heard in a laptop. Touch ID works very good, I have had no problems so far.
Now to the bad parts. Performance is my biggest complain. I got 16 GB machine and it is slower than my MBA 2013, which is not acceptable. It is perfectly usable 99% of times, but it just doesn't feel as good as old MBA. Most operations require micro-lag, which feels like some random Asus. This was one of the main reasons why I loved Apple, because their hardware/software was smooth. It's not anymore, at least for this MacBook. Some people can't tell the difference, so I guess it's not that terrible, but if you are really a user-experience junkie like me, you will feel like it's a massive downgrade. It also gets hot way too often and the fan starts sometimes even with some softcore tasks. Next, battery. I don't know where did Apple get 12 hours from. For me, the battery goes down pretty quickly. It's annoying when I'm watching video on YouTube and I see like the battery is running out. And that's with Bluetooth disabled, keyboard backlight disabled, screen dimmed to half. I will never trust any claims about battery life from Apple anymore. The battery is clearly a downgrade from 2013 model's and they still call it better. This is just outrageous, even by Apple standards. The aluminum quality is not the best neither. I carry my MBA like a baby and I once accidentally hit it against the wall while it was in a soft case. It wasn't a hard hit, but it left mark on the corner. I imagine how it's gonna look like after several months for people who are not that careful with their hardware. The keyboard backlight looks really bad. It's so uneven, looks like some Chinese crap. It's especially obvious after looking at the space bar. Awful. USB-C cable quality is bad too, it looks very cheap, while obviously being expensive. Apple way. I feel uncomfortable while plugging and unplugging it, it feels like it can break any time. And the last thing, I wish they made the touchbar a little smaller. The space between keyboard and touchbar feels kinda weird - it's either too big or too small. In my opinion they should either make touchbar start almost directly below the keyboard, or leave the gap like in previous models. They wanted to make the touchbar as big as possible, which is cool, but this gap is poorly designed.
That's my 2 cents after 2 months.