I believe the recommended weight distribution is 60% in front and 40% in back. I did try to get as close to that as possible ... stuffing whatever I could into my carradice (nelson long flap) on my rear rack, but I usually ended up with a bit more of the weight in front.

Yes, it does affect the handling ... it makes the bicycle so much more stable. If you've never ridden with a bicycle with that amount of weight in the front before, it will take a ride or two to get used to it ... and things like standing out of the saddle on climbs takes some practice, but once you get used to it, when you ride without all that weight ... the bicycle feels really twitchy. There were only two places on my Australian tour where I had difficulties with the load in front ... one was on a particularly steep descent ... I felt like the rear wheel was coming up off the ground!! It probably wasn't, but that was the feeling I had. The other time was crossing the bridge in Hobart. That bridge is long, and the wind was just howling off the ocean - a crosswind. With that much bulk in front, blocking the wind, I was thrown all over the place. I ended up walking across the bridge because I couldn't control the bicycle.

If you look at the photos of my tour of Wales, I had the bulk of the weight on the back of the bicycle because I didn't know any better then (that was my first loaded tour), and it just didn't feel right ... especially on climbs!