I managed to upload a model to the 3D warehouse and then download it back to my machine. If you have sketchup on your machine you should be able to find, download and orbit/edit someone else's model.
The only thing I haven't figured out is a specific web address for the models. The model I uploaded is called "mark's cruck"

To upload a model:
save a file in sketchup.
clic the file menu
choose "3D warehouse" then choose "share model"
This will open the 3D warehouse and you will have to log in if you don't have a google I.D.
once you are logged in, just name the model, etc and upload your model.
The only problem I can see is the lack of specific web address, so if you intend on sharing the model, name it appropriately.

To download a model:
open sketchup, clic the file menu and choose "3D warehouse", then choose "get models"
This will open the 3D warehouse
If you'd like to find the cruck below type "mark's cruck" into the search box.
clic "download model"
This will download the model straight into sketchup, even if you have a drawing underway... you may want to open a new sketchup file.