It really is a tossup for me. If I don't pull it back, sometimes it'll balloon for a second then go everywhere like Ohioguy said, but other times it will be perfectly straight and fine. If I do pull it back partially, it's pretty random whether it helps or just makes me piss in random directions. So, I suppose it really just depends on my mood and the current situation whether I pull back or not.
Funny story I just remembered--I was at my dad's one time, chilling with my step-brother and one of his friends, and I had to take a piss. Step-brother's room=right next to the bathroom, with paper thin walls. I was in a hurry, so I didn't retract and was forcing it out. When I got back, they were both laughing and said something about sounding like a waterfall. (Both of them being cut (I think) and having no idea of the mechanics)
My face when I was embarrassed, and knew that I couldn't explain it. ^^;;