My boyfriend and i have just bought our second IS200 Sport, We bought the first one when he was 23 and i was 19, I think the car would suit any age group :D
Do you know which model of the IS your going to get? I would recommend a sport :) Finsing one with low mileage will be a task but if you read other topics you'll find out that high mileage on these cars really isn't an issue if they've been well looked after!
Good luck with your search!