I had an IS200 LE for 4 years before moving up to a 2nd-Gen model, and had also owned a few BMWs previously, and for me an IS200 can indeed be fun to hoon around in.
Despite being fairly slow, the car's fundamentals - very nice steering feel, decent 6-speed gearbox and RWD chassis make it fun to drive on country roads.
My own car had a lowered & widened stance that made it feel even better in the corners, otherwise it was standard.
So yes, even with a modest 153BHP, an IS200 can be a fun car to drive.
One thing I will say though, is that the auto should be avoided. I eventually sold my IS200 on to a friend, who also later picked up an auto one.
He told me that the auto box kills off a lot of driver appeal. They're also incredibly thirsty compared to a manual one.
If possible, I would follow Colin's advice and go for an IS300. These are also automatics, but have a lot more grunt and an extra gear to play with. And also, some semblance of manual control via the steering wheel buttons.