I haven't bought any models recently as run out of space but I couldn't resist buying some more XL when there was a 3 for 2.
As already mentioned the Runabout is lighter than it looks, the bottom and top are metal but the main body is plastic. The model itself looks fantastic and extremely pleased with it.
The Bird of Prey is a very solid weighty chunk of metal but was just a bit underwhelming for me although I can't put my finger on why.
The Enterprise C is a very nice model, although the plastic used for the deflector is too transparent so you can see the post behind it joining the two parts together.