I bought my 2001 Insight earlier this year with only 6500km on it. I have not experienced any problems that might be caused by limited use during its first four years of existence. Seems to me that this car is a great buy.
Proceed with caution - it may have been in a serious wreck and was recently fixed. I've run across this before thinking I found a low mileage gem but actually found a cleaned up lemon. I would do some serious investigation before signing the papers on this one.