For a long time I thought a cart was just a tray with wheels, the kind of thing you'd buy because the aisle was there and the price was low. Mine was thin metal, it wobbled if you looked at it, and the wheels locked up with dust within a month. What changed my mind was standing one next to a secondhand bar cart with a solid wood top and actual weight to it, and feeling the difference in about two seconds of pushing it across a floor.
A good cart earns its spot next to a reading chair, at the end of a kitchen counter where you need a bit more surface, or in a bathroom with no storage to speak of. It sits well near other things with a bit of warmth to them, wood, woven baskets, a plant that needs moving toward the window twice a year. It does not need its own moment, it just needs to be useful, which is the whole point of something on wheels. In an ordinary room it works best filling a gap nothing else quite fits, rather than trying to be the main piece.
The day it arrives, check the wheels before anything else, give it a push on the actual floor it will live on, not the showroom carpet. Cheap casters catch on rugs and scratch hardwood, good ones roll quiet and straight. Check the shelves sit level and don't flex when you put real weight on them, a cart that bows under a stack of books or a few bottles is not going to improve with age. And look at how the frame joins the shelves, welded or bolted feels different under your hand than glued, and you will know within a year which one you bought.
Where it goes wrong is tight hallways and anywhere near stairs, because a cart with any width to it becomes a hazard the moment someone's carrying laundry. It also clashes in a room that's already busy with other low furniture, a cart needs a bit of open floor around it to read as useful rather than as clutter you're rolling from room to room. And skip it entirely if your floors are uneven old boards, because even a good cart will lean and drift toward whichever way the room settles.
The detail that makes the good ones worth having is the sound, or rather the lack of it, when you roll a well made cart across a wood floor and it just glides, no squeak, no catch, no little performance of dragging. You stop noticing you're moving furniture at all.