I currently shoot a .029 is the .019 worth the extra money when upgrading a sight. Also since I am upgrading my sight should I go with a single pin or a multi pin I hunt and target shoot.
Scott, I found the .019 pins to help me shoot better beyond 25 yds. I still have pretty good eyes, but for some reason the .029 pins haven't worked real good for me for about 5 years now. I switched to the .019's this year and have been happy. As for the single pin versus multi pin, I just use two pins on my sights, a 20 and 30 yd pin.
I still prefer a multi-pin for hunting and of course target shooting. Really comes down to visibility and use. I have good vision, so I like to use .019 for my 20yd, then .010 for everything there out. I find with my eyesight, the .019 and larger tend to cover too much 30yds and out. For spots, a bigger 20yd (or top pin...whatever yardage you may if sighted in for) tends to help cover the X and cut down on mental focus off the pin float (for me anyways). If your eyesight isn't great, I definitely wouldn't shoot .010 pins, but I think even a .019 all across the board would work as a general rule.
I have never seen a cost increase to get the .029 pin from a .019 (but I've never paid a huge amout of attention). .019 is now pretty much the standard. I would definitely go with the .019. They give you a better picture than the .029 but don't fuzz out as bad as the .010 pins. My vision is perfect and sometimes it's hard to focus on the .010 pins unless they are very high quality pins.