The question was never really whether Tiger would play well in his return to the PGA Tour (of course he would), but whether his swing would change. The answer to that question is yes. Tiger has made a slight adjustment to his action through impact, relieving some stress on his reconstructed left knee. That's good news for Tiger fans, and bad new for the rest of the Tour.
Tiger has narrowed the width of his stance when hitting iron shots, which lessens the stress on his knee. With his feet closer together, it's easier for him to get his body on top of his left foot at impact. Slightly flaring his left foot also takes some strain off his knee as he rotates to the finish.