The smudged look generally appears when distant areas show up on screen, such as the other islands across bodies of water. The graphics are definitely a good improvement over the previous entries, and the game can look quite nice in instances, but there are definite graphical compromises required to get such a large, streaming environment to work. I kinda blame every gaming website which has separate ratings for graphics and rated it a 10 - people are going in expecting the graphics (technical & image quality, not style) to exceed those in games where more "manageable" environments are used. (Another reason against numbered ratings systems, but that's a discussion for another thread)
Speaking of bodies of water. One way to get an instant 6-star wanted rating is to try to swim to the "locked" islands.
Got a 4-star when I entered the airport grounds thinking "lol security", but then climbing a ladder up onto a building triggered swat teams being sent after me. I guess jacking a plane might not be that easy.
So far I think the best part about the game are the characters and the written/spoken parts. Vehicles are perfectly fine, though you have to consider that each handle differently - choose wisely. I haven't spotted something like the scooter from vice city - handy little bugger for exploring.
Haven't tried multi as the servers are down.