First, shooting and scoring...
Williams is a couple of slightly higher-usage, hot shooting games from being essentially the same offensive player he was last year.
Rebounding, passing, ball-handling, and defensive box score stats...
As for on/off defensive stats (in terms of team Defensive Efficiency)...
A negative differential being good in this case, the Hawks, despite being a slightly worse defensive team in the early days of this season than they were last season, have been better than last season when Williams is on the floor.
Overall, when put in context and acknowledging the extremely small sample this season provides, Marvin Williams isn't off to a slow start so much as Jamal Crawford and Maurice Evans are off to hot starts. Should Crawford and Evans continue to play at the high level at which they've begun this season that may mean that Williams, even if he matches last season's production on a rate basis, will not match last season's playing time* but more Hawks being as productive as Williams was last season isn't exactly a recipe for disaster even if it is a recipe for Williams to post superficially disappointing individual stats.
*On a per game basis, that is. One hopes for better health for Marvin this season.