I think a great thing about the current theory of gravity is how well it models orbiting of bodies. I saw on TV at one time they had a carpeted room with a ball, earth, on the center. This floor was shaped as if the "earth ball" had sunk it somewhat. Then they grabbed another ball and they threw it with some speed into the region of the "earth ball". Because of the curvature of the floor, the trajectory of this other ball wasn't a straight line but actually went around the "earth ball" a fair amount of times (while keeping the same distance from the "earth ball"). I thought this was very cool, and i can imagine that without the friction of the carpet and air resistance and all that stuff, the ball would keep orbiting the "earth ball" for a very long time.
This i think is Eistein's model of gravity, with the curved flor being curved space-time. This model works really well, it explains the orbiting, explains the acceleration, and explains why bigger objects have more gravity.
I believe that this model is really the best we can have, but i have some questions on how it's "implemented" in reality. For example, if the ball weren't under the effect of Earth's gravity, it wouldn't orbit the "earth ball" at all. Also since the floor (space) is 2D, these balls wouldn't be spheres but actually circles insided the carpet, which doesn't necessarily change anything. In reality a body like the "earth ball" must curve 3D space, which i don't have any objections with either. The main problem that i see is that we're explaining how gravity works by using gravity. For example why does the "earth ball" curve the floor? It wouldn't if the whole system weren't under the influence of gravity. The other ball also wouldn't orbit the "earth ball" without the influence of Earth's gravity. I know this is only a model and models don't have to exactly correspond to reality, but it seems that gravity is a force that's coming from outside our 3D space?
For example, consider a plane here on the surface of the Earth that is sunk down in the center. Suppose this is a 2D universe and i have 2D objects inside this plane. As the 2D objects inside the plane get near the bend, they are accelerated. You have to imagine you're inside the 2D plane, you don't know that the space is bent, but you feel the acceleration. This acceleration is actually due to the gravity, not stemming from within the 2D system, but from our 3D world that this 2D model is on. So it's interesting how an n-dimensional system's gravity produces the effect of gravity in an (n-1) dimensional system.
So our 3D gravity may be an effect from 4D gravity, which is an effect from 5D gravity etc. If this is the case then i can see how gravity is hard to explain, because it is coming from outside our 3 dimensions, so it' hard to theorize on that. However, if we assume that this is the case, then we have Einstein's wonderful model to explain our gravity.
I found it interesting when i thought of it, but then while i was in the shower i saw droplets of water running down the wall, and i thought "how can the theory explain that?".