they're almost compact - a bit larger than compact but not even CLOSE to dslr size.
size - 109x78x46mm. it's too big to fit into pockets really but is otherwise completely fine. doesn't weigh too much either.
function - don't worry about the differences between g10 and g11 here, the g11 will actually produce better pictures despite having fewer megapixels.
usability - yep, that's fine, you just select Av and pick your desired aperture, and everything else falls into place.
it's pretty nifty, a bit shit at higher ISO but if you have enough light then definitely a winner. i've got the g10, if you scroll up the page, i posted a bunch of photos i've shot with it. have since lost mine tho, gutting.