We have one that came with the house. I'm sure it's at least 40 years old. It was clearly cut in after the slab was poured, they used concrete block for the walls and didn't reinforce them. Still, it hasn't caved in yet.
For me the biggest downside is not having a good place to jack the car up in the center when the wheels need to come off. I do have a way of doing it with a bottle jack and a steel column, but it's a little iffy, it's slow because the stroke of the jack isn't enough to do it in one shot and and I only just have enough space to set the jackstand so it's clear of the edge of the pit yet still inwards enough to be able to grab the subframe. If you don't mind using the pinch welds to jack the car up or set the car down on, this would be less of an issue.
Height? Ours is a little short for me if the car is on the ground, okay when it's on jack stands. Better to be too deep because you can always add wood and a rubber mat to stand on.
Another problem is the water table. I had to install a sump pump because it will sometimes have six inches of water in it after sustained rain. I also had to cut a trench into the concrete to run the drain line to an outside wall (but this allowed me to run a conduit for future electrical). I should have run an air line too but I was in a hurry to get the concrete done before the winter.
You also have to straddle the pit every time you put a vehicle in that space, a pain if it's a 1-car garage, which ours is. At times we contemplated filling it in for this reason.
Yes, going up the steps to retrieve tools is a pain. The best solution to this is to have a helper. You could also put storage in the pit but at some point it may be in the way.
Lack of light is another problem. I did buy light fixtures to aim upwards but haven't put them in yet. They'll need to be protected from impact and chemicals and I'm still working out how I'll be doing that. For now I use a halogen work light on a tripod.
Advantages? One thing that I really like about using the pit is that if you are doing a job that needs access from both above and below, you just go up and down as you need to, the car stays put. Also, easy to get someone to get in the driver's seat and pump the brake pedal, turn the steering wheel, turn the engine over or run it while you're underneath doing whatever.
I would put a pit in a future house, yes, but I would make some changes.