Good is relative, and situational.

A big part of why it's good is that it's familiar and you're probably already registered.

Indeed. I remember having a quite frustrating time convincing Amazon to ship to my work address, as for some reason it didn't fit its understanding of what an address should look like and it didn't "validate". The address is not even that uncommon (it's just not on a street/square/etc. but on a campus, and has no building number), and I never had that problem in other websites.

But that was years ago, now the address is already registered and it's not something I remember every time I shop there. Instead, what I experience every day is a very streamlined checkout process (the only small frustration is that the option to "group shipments into a large shipment" seldom appears now. The other day I bought two little boxes, identical except for the color, for about maybe €9 each, and they shipped separately, which is a bit jarring).

You say that but - their search works really well. Most other shops it’s awful. You’re lucky if it can even correct spelling errors.

"Really well" is overselling it quite a bit. I can search for the exact product name as displayed on a product page and still not have it find hits. Ebay's search is quite a bit better.