I heard in the postgame analysis that the Celtics are 5-0 in the playoffs when Ray scores 18 points or more... so our success is critically linked to Ray's offensive performances.
I agree that Ray has been playing his best basketball as a Celtic in the 2nd half of the season and in these playoffs, even better than in the Finals in 2008 (more consistent and on the longer stretch) or than against Chicago last year, even when he exploded for 53 points (if I recall the number correctly).
He played with a hamstring injury against Orlando last year, it affected his play, but also this year he is playing with better teammates (Rondo has improved and KG is back) so it helps him get better shots.
Also, he is in great shape, as always, but Doc's strategy of limiting his minutes during the season and keeping him fresh from February to April paid off in my opinion. Last year, at this point Ray played with all the fatigue and common injuries of playing about 43 minutes per game in the 2nd half of the season, not to mention the fatigue of the 7 game series and multiple OT against Chicago. Big difference for a 34 year old shooting guard.