+1 for Dave Richards's stuff.
He's a woodworker, and understands both SU and the nature of the tasks in woodworking design/construction. Have a look at his blog on the Fine Woodworking web site. There's a huge amount of gold there.
Roger is quite right, for example, components are THE way to work. Dave has also helped me in the past with quirky things like making 3D curved surfaces in SU, and how you make one object modify another.
SU has some built-in limitations (everything does) going back to its origins. They're decisions about how to do stuff, which have set precedents and then stuck. Microsoft Windows is just the same. These problems can be overcome, but for success and freedom from headaches at crucial moments, you need to know quite a lot about what's going on under the surface, which Dave does.
I'm in two minds about whether SU really is easy to learn, or not. My children used it in school. They could draw a 3D house with windows and a chimney in five minutes. When they saw I was using it they were a bit dismissive, on the basis it was a very simple thing, a toy.
As far as I can tell, the way it's used in "ICT"* lessons seems only to be illustrative, "This is how you can use a PC for 3D modelling," rather than getting into the detail, to really make it sing. I doubt their teachers are able to do it, anyway. If I had a problem, and asked the kids, "Did your teacher show you how to do...?" The answer was usually that they hadn't tried that. Then they lost interest in the conversation.
It's deceptive. I don't think it is particularly easy to use. To get good results from it, you do have to learn workarounds for bits of it that don't work particularly nicely. On the other hand, it's the 3D equivalent of Acrobat - everyone has it, so things can be shared and recycled in a way that's pretty much impossible with the likes of Autocad. But the free version is easily good enough to make workable designs for woodworking. I use it to resolve design problems that I can't get right in my head, such as odd joints (I did a weird M+T one for the garage window frames that seems to have worked well). And you can get it running on most platforms (I run it on a Linux box). And it is free.
Have a look at Dave Richards's stuff. You are very unlikely to be disappointed.
E.
*"Information and Communications Technology" educationalists always try to make simple things obscure - it's job preservation!