Although I'm dubious about how fast one could get up to speed with it, it does look like they did some hard things right. The app looks like a lot of other drawing tools (e.g., Adobe products), offering a big palette of modal mouse tools; and there's a persistent "help" text on the bottom telling you what to do and what key combinations extend the function of the tool (very Adobe-esque). It's the keyboard shortcuts, of course, that would be the hardest to learn as a new user. Once you know those, you're probably focused on the art and not the mechanics, which is what you want in any creative activity.
They've got a clever function for "bookmarking" important views of the buildings for showing clients; they have a nice shadows-by-time-of-day slider bar that looks fun to play with; and they give useful feedback during drawing via tooltips that pop up to tell you what your current status is while you're manipulating the building and objects ("on face" etc.). You do still need to know something about physical objects -- to create a roof from a flat surface, you have to know how to draw the joints that will bend in the right form when you move the lines upwards. All the connections are "smart" and pieces move as units, but you've got to know what you're aiming for, too. (Just like when using Photoshop -- if you don't know what saturation is, you can't use that tool well).
Perhaps most compelling of all, there are downloadable plugins and scripts and "components" (like trees and buildings and people), reminding me of extensible game worlds like the Sims. I'd like to get them together -- my problem with the Sims is that I don't want to start with a white trash shack and build up to a good life, I want a beautiful mansion right from the start. And their building tools aren't so hot, either.
I digress -- SketchUp is, alas, $500. I may still try the free trial, good for 8 hours.