I rushed sophomore year - we had deferred rush anyway, but I was pledging APO my 2nd semester freshman year. Because of that I was WAY ahead as far as knowing the Greek alphabet, time commitments for pledging, etc.
I am SO glad I did. I didn't get burned out and I made a lot of non-Greek friends, and knew people when I went through rush, which really helped to know a face or 2 when I walked into the room. Plus I got to see the women in my dorm go through sorority pledging (not to mention little sister pledging, if I had thought of exploring that option) and that also was a help.
DISCLAIMER: If your school has a BIG Greek system where 98% of the rushees are freshmen, don't listen to me!