Wall lights are the fixture everyone skips and shouldn't. A single lamp in the corner is doing one job, lighting a chair, while a wall light up at head height changes how the whole room reads, because it's light coming from somewhere other than the ceiling for once, and that alone makes a room feel less like an office.
Mine have held up fine over the years, finish wise, though the ones with any brass or bronze in a bathroom will show water spots if you don't wipe them down now and then, and fabric shades near a kitchen pick up grease faster than you'd expect from something bolted to a wall. Dust them the same way you'd dust a picture frame, a soft cloth every month or so, and check the bulb isn't running hot enough to yellow the shade from the inside, which happens more than people admit. On sizing, the mistake I see constantly is hanging them too low, like eye level in a hallway, where every guest gets a direct hit of glare. Center of the fixture wants to sit around five feet to five and a half feet off the floor in most rooms, higher if the ceilings are tall, and you want at least a foot of clearance from any doorframe or mirror edge so it doesn't look like it's elbowing something else out of the way. For a pair flanking a bed or a fireplace, measure the gap first and then measure again, because a light that looks fine held up by one person is often a few inches off center once it's actually mounted and you step back.
Before you buy, check what's behind the pretty front plate, because some fixtures hide the wiring box in a way that makes installation genuinely awkward if your wall box isn't in exactly the same spot. On delivery, check the shade sits straight and isn't cracked where it meets the arm, that happens in shipping more than you'd think, and check the dimmer compatibility is printed somewhere, not just assumed. As for where they go wrong, don't put a strong, busy patterned shade directly above a patterned wallpaper, it's too much happening in one sightline, and don't put a tall upward facing fixture under a sloped ceiling unless you enjoy a weird shadow triangle every evening. Stick to one finish per sightline too, mixing brass wall lights with chrome switch plates in the same wall reads as an oversight, not a choice.
Get the height and the finish right and a wall light does something a lamp never quite manages, it makes a room you've lived in for years suddenly look considered.