I don't think it's a bad trade for Boston even with the #5 pick, because it makes it clear that Boston wants to win now.
They would give up Jefferson, but it's more than likely he'll NEVER be as good as KG. They give up Green, but he couldn't crack the lineup in Boston and they have enough G/F to make up for him (Tony Allen, Allan Ray, Szerbiak, Gomes). Telfair was relegated to third string because of West and Rondo. And don't forget Paul Pierce, who is underrated at this point.
Here's the Depth Chart:
PG West/Rondo/filler
SG Pierce/Allen/Ray
SF Szerbiak/Gomes
PF Garnett/Scalabrine/Powe
C Perkins
Keep in mind, they could still go out and sign someone and Garnett could play Center as well. Play KG and Pierce for 40MPG and let the rest sort itself out....