I used to use a vest, now I use convertible hip pack made by 'Fish Pond' This model can be worn in front as a chest pack, to the rear like a fanny pack or off the shoulder as a side bag (my favorite). It holds all I need for a day trip. I should also mention that I use a lanyard for my tippet and tools and wear a fishing shirt with big chest pockets.

http://www.fishpondusa.com/blueriver.cfm

I was happy with a vest for many years, but it was difficult to use with a PFD (life vest) while boating, the vest was awkward to wear with a heavy coat or rain jacket. I sometimes needed to take the vest off to get at the rear pockets. The vest holds too much gear, I would load up all the pockets and end up carrying a whole fly shop on my sorry back. I'm put off by the high price of some vests, $150 plus seems like a lot of cash for a simple vest.

I agree with the other comments about chest packs and vision. I rarely wear my fish pond in the front, it prevents me from seeing where I step. Worn on the back or side I can flip it around to the front for access as needed. It has a low enough profile that I can wear a day pack with it for longer hikes. I can't comfortably wear a day pack over a loaded fishing vest.