There are known convertible top issues.
Resources for the Repair and Maintenance of your 2005 Honda S2000
2005 Honda S2000
2005 Honda S2000 Problems
A problem can occur with a vibrating expansion valve in the AC system which causes a whistling noise from the passengers vent. Replacing the expansion valve with an updated valve from Honda should repair this problem.
Some S2000's can develop a problem with the transmission popping out of fourth gear. A new updated fourth and fifth gear assembly will repair the problem. The transmission will have to be removed and disassembled for this repair.
The S2000 is set up with aggressive alignment settings and soft tire compounds to enhance handling. These alignment settings and soft tire compounds result in tires wearing out earlier than anticipated. This is a compromise made to have a car with exceptional handling characteristics.
The MAP sensor contacts can shift at high RPM causing a hesitation. Replacing the MAP sensor will repair the problem.
2005 Honda S2000 Reviews
Ours has 18,000 miles. Rear tires will need replacing within the next 5000 miles, or less. On cold days with top down, there is a special heater blower setting to keep the passengers toasty. An excellent car. Cup holders don't hold the cup. It can fall over, literally, when you accelerate. Also, two cups don't fit unless they are very, very slim. Other than that, it cannot be improved. I couldn't hear the engine which made driving by "sound" impossible. So, I had the resonator removed. Gave it a little more "tune" which is just right. This fix was recommended by many other owners who had the same concern.
Fun to drive. Great value for the price. Performs better or as well as cars costing much more.