^^^More noticeable yes but I wouldn't say uncomfortable in either case. If you are coming from the 18's I would suggest going with a 16'' package simply because it's less drastic. There have been a few guys on here that were unhappy with the difference on a 15'' set.
Refer to 'Miles/FocusFanatics' as your previous contact when you order online. You can also credit the forum by ordering through any Tire Rack