Off Topic: Haarlem is by no means the only IKEA in the Netherlands, nor was it the first. Having lived there, and hauled half my furniture 45 mins on a train, trust me on that. I see the IKEA there is no just about 5 mins from my old home - oooooooh, how I could have used that. LOL
Karen, Haarlem is great if you love shopping. As others have said, the Barvo Kerk and the Hiding Place (ten boom museum) are worth seeing. The town center is one of the older ones, dating back to the 1200's in places (buildings still in use today).
If you go on a Thursday, there's late night shopping. Great night to have some ice cream, sit at a cafe, and people watch.
Saturdays have a nice market in the main square, that is worth going to.
As I mentioned, shopping is the main thing in Haarlem. It has lots of modern stores. BUT, if you go off the beaten track a block or two in the town center, you will find wonderful oooooooold shop, still making candles, and violins by hand, etc.
I don't know that I'd spend a couple days there, but I'd definitely do one.