My first El Cap route was Zodiac, January 2010. My second was the Nose, late March 2010.
On Zodiac we battled a runoff waterfall that ran around the clock. On the Nose we were hammered by snowmelt runoff every afternoon and evening.
You'll find more answers at bigwalls.com than you will here. Here's the thread I started before I went up Zodiac:
http://www.bigwalls.com/forum2/index.php?PHPSESSID=c137c9ef89e28dc5d636561a2b9690c2&topic=794.0
Martin Fickweiler posted a video in it, I highly suggest you watch it. It's in Dutch, but you can tell they're getting rained on when they have their hoods up.
Also, Mike's advice was spot on:
Dealing with that runoff was miserable, and really tested me.
I didn't have to deal with that, or falling ice frisbees. But I was up there in relatively warm conditions.
Coming down from the Zodiac was easy. Coming down from the Nose sucked as there was way more snow. I brought a waterproof OR bivy sack, but the condensation slowly got through over the course of the two wet bivies. My down sleeping bag was saturated and useless so bivying would have been miserable. We had to descend in the dark. We would have had problems if I didn't already know the descent. If you need to, leave your stuff on top and get the fuck down.
Zodiac trip report:
http://mountainproject.com/v/trip_reports/tr_gumby_winter_ascent_of_zodiac_el_capitan/106669167
Nose trip report, written by my partner:
http://cheynelempe.blogspot.com/2010/04/my-first-big-wall-and-my-first-trip-to.html
Top of Zodiac. There's almost no snow up there. If you look at the end of Martin's video, you can see 2-3 feet of powder.
I went back in summer and crushed "Nose in a Day." Really, really fun, and way easier than my first two times up.
I hope this helps! Let me know if you want me to expand on anything.