most shops will throw it on the alignment rack for free if you ask em' and check it for ya if you think you didn't mess it up when you put in the new struts...but an alignment can't hurt...
Before I took off my old struts, i marked the location of the stock c/c plates lightly with a pencil. Then when I was putting them back on it i lined them up. I got it aligned anyways, but the guy told me that caster/camber were good, just the toe was off a little.
But like everyone else said, if you havent had the car aligned in a while, after you pit your struts on might be a good time.