Wood – like a door, but with a groove and two holes

I have used MDF for a number of furniture building applications. Shelving, cupboards, cabinets (body and doors).

1. It is easy to work into interesting shapes, you can cut curves using a jigsaw and sand it easily.
2. If you sand off any of the surface, and on the cut ends, you get a very different finish than on the front/back surfaces. If you want to get a smooth uniform finish I suggest using an undercoat of acrylic or PVA. If you are careful and get the undercoat right you can get a very smooth (almost plastic looking) finish.
3. Best to avoid damaging or removing the surface, as the surface is quite different to the inside and may contribute to the strength (not sure).
4. I usually sand over and round any exposed edges to prevent then from getting damaged. I always finish MDF with some kind of paint, so the texture differences are hidden.
5. MDF is very dimensionally stable, I have had no real issues with it changing size due to temperature or moisture
6. Basic MDF is not very good at handling high moisture levels. I always try and seal it as far as possible using a paint with relatively high moisture retardation (couple of coats of gloss paint for example). I have not so far experienced any serious moisture damage to my MDF even in places I have used it as an experiment in my kitchen where it is exposed to humidity (replacing chipboard which was being damaged by the humidity). However, it has only been a few years so I will see how it is in another 10.
7. Use exterior grade MDF if your application is likely to be exposed to high levels of moisture.
8. I often fix it with wood glue and dowels, but screws will work fine as long as you drill a pilot hole.
9. MDF is not as strong as plywood, if you are using it for shelving/load bearing you will have to increase the thickness compared to plywood or use some other method. For the sides of cabinets, etc, I have sometimes used two pieces attached face to face.
10. the dust from working it is a bit horrible, so wear as mask/use extraction

Overall, it has some advantages and some disadvantages. I think it is rarely the best material, but probably good enough for a number of furniture building applications. And for some things (like cutting into shapes with a jigsaw) it is very handy (no grain). I have not so far had any serious durability issues, but I do always take the above precautions.

You took the wind out of my sails with that last paragraph. I was going to suggest using a nut/bolt.

As far as it causing problems when the tabletop is lowered, you can recess the bolt head. Yeah, you could make the cavity in which the bolt will stay on the underside of the tabletop, but maybe you'll drill too far or crack/scratch the tabletop if you chisel it out. It could end badly... which is why you should instead house the bolt head on the top-side of the cross member.

Brown = table top
Black = underlying cross member

The one on the left is what you were talking about. The one on the right is what you want to do.

Also, use a washer under the bolt head, etc.