Never used a Syncpack but I have logged quite a few miles with a Dana Designs Wet Rib ,which is not nearly as big.

Yep, it's nice to have easy access to some of my stuff. I didn't buy it to distribute the load because my load is usually not very heavy. It has 3 distinct disadvantages:

1) It's hard to bend over to tie your shoe or pick something up.

2) If your route involves class 3 scrambling, crawling, or even a few tight squeezes, a chest pack becomes a liability.

3) It's hot and it makes my chest sweaty.

That being said, the wet rib does shine in cold weather when #3 is actually an advantage. And it's great for gloves and hats on those days when the sun is in and out of the clouds and the temps keep changing. My Wet Rib has been relegated pretty much to Winter use.