The driving really isn't bad..... And even better if you use some navigation since a lot of the streets are one-way. But no problem whatsoever, it just can be a little crowded at rush-hour. I commute to AMS almost everyday :-).

But I also feel that for a visit to Haarlem from Amsterdam a car is about your worst option. The train lands you right where you want to be, in 15-20 minutes, about the time you would need to just find a parking space.

The rest no problem..... Just count on €4 an hour to park :-(.