I just did this exact switch you're asking about: from 18s to 19" staggered on my 4.4i. And Iit was with the Michelin Latitude HP all-seasons.

The verdict is still out, since I only did this a couple of weeks ago. I ran into some bad luck with the tires: the dealer gave me 3 out of 4 tires with cracks in the sidewall, and then tried to pin it on "road hazard". I took them to task and had them put on a 2nd set at their expense. We'll see what happens. Cosmetically, it looks nicer than the 18" setup. I have no idea how these Latitude all-seasons will do in the snow. They do say "M+S" on the sidewall. Time will tell.