Let's not forget that basketball is a team sports. With that said, Rondo, as terrific as he is for the Celtic's, lacked the perimeter shooting that is needed by the team. Just like what was mentioned in this forum post earlier, Kobe during the finals laid-off Rondo and dared him to shoot. With CP3's jumpers, means Kobe (or whoever is assigned to defend the 1) will have to defend better. With CP3's offense, it will only help the low post offense of KG, Pierce (at times in a mismatch), JO, & Shrek.
Also, someone mentioned that with CP3 on board, he "might" attract more marquee FA's in the future. That is true, too.
So, "if" the trade is made, and the popular choice is to include Okafor, I think it's a really good deal to make, in my opinion.