It's not good in my opinion. Lewis and JJ will not play the same position but it gives the Magic a surfeit of what JJ does best: three point shooting. Looking at the Magic's roster right now, they have a logjam of potential two guards.
Starting four:
Jameer Nelson
Rashard Lewis
Dwight Howard
Darko Milicic (if they can resign him, which they really want to do)
Here is JJ's competition for the two spot/3-point specialist:
Hedo Turkoglu
Pat Garrity
Reshawn Terry
Keith Bogans
What's worse is that the Magic also have a bunch of backup point guards who can shoot (not nearly as well as JJ of course, but still, they'll take up minutes):
Carlos Arroyo
Travis Diener
Keyon Dooling
With the addition of Rashard, it gives the Magic more flexibility on the floor. Instead of having another shooter to complement Jameer and Rashard, they can opt for a slashing athletic two like Bogans or maybe even someone bigger like Trevor Ariza.