Really nothing wrong with balsa pushrods, if the piece of balsa is both straight grained and fairly hard (firm). The good thing about using balsa is that it will often snap in a bad crash and the damage to the servos is reduced. You can file a slight groove in the side of the rod, from the hole to the end and insert the wire end. Then hold the wire with a bit of CA and wrap with any of the following - thread, monocote, or heat shrink tubing.

On really fast airplanes (above 150), I switch to 1/4" hardwood dowels.

I've also used the methods mention by khodges with great results. I try to match the level of technology to the requirements of the airplane*. Most important is to plan the control system early in the construction, and avoid any bends that will flex to the flight controls. Often for best results, you will want to cross the pushrods to get a straight shot at the horns from the servos.

*Don't put a $1000 saddle on a pig and expect to win the Kentucky Derby.