I had a very good rental from ADB with Holiday Autos and would just say remember that some of the road surfaces are very smooth and thus if it rains you may have problems of grip. Other than that, no problems at all.
I would suggest staying at Selçuk (pronounced Selchook) instead of Kusadasi because it is a proper Turkish town and Kusadasi has far more tourists and cruise ships and I found it far less 'authentic' and Selçuk is handy for visiting the hillside winegrowing village of Sirince (See rin chay) and the Steam Loco museum (excellent) at Camlik (cham lick).