Been thinking about this alot myself. Glad you brought this up as i think it should be easy to test different themes but its a giant hassle. Canvas theme offers heaps of shortcodes for starters that wouldn't work if you changed themes.

I switched from Thesis to Canvas and all my sub headings got messed up and i lost images so i'm looking forward to reading the guide from Konstantin Kovshenin and appreciate the effort he must of put in to put it into a guide.