Robin Williams is great no matter whether he's acting the fool in a stand- up routine or whether he's playing a serious role. This one leans toward the serious side, although the movie has some really funny scenes. The one with James Earl Jones as the pawnbroker is borderline CLASSIC. Jones shows a comedic side I've never seen before -- actually had to rewind and replay that scene twice and laughed as hard every time.
Not Williams' or Kunis' best roles, but definitely not a time-waster. Williams can make even the plight of a man nearing death seem funny, and Kunis is easy on the eyes no matter what role she plays. Melissa Leo is always good, and this movie is no exception. And the guy who plays her sometime-lover, Bob Dishy, is probably the most "unknown famous actor" in the business. I KNEW I had seen him before, so I googled his name, and found that he goes all the way back to Barney Miller. Never knew his name before, but he sure is a familiar guy.