Lego says I can I use the new software to program old NXT bricks:
Q: Is EV3 backwards compatible with NXT hardware?
A: Yes. You can program your NXT intelligent brick using the new EV3 software. However not all software features are supported by the NXT intelligent Brick. You cannot program your EV3 programmable brick with the NXT Software.)
Are there any known limits programming the NXT bricks? I often had problems with MINDSTORMS NXT under Mac OS X and would like to replace it if possible.