Recently I came across a useful visual guide to removing the underwires on a bra. You might want to consider removing the wires on your bras if you find them painful, like the small-busted woman who posted this guide; she has a hard time wearing underwires because of the way her ribcage is shaped. Her method of taking out the wires does not require any sewing, which is great for those of us who suck at it.
Be aware that with the wires taken out, the fit of the bra cups may change, which you can see in the before-and-after photos of this woman in a Natori Feathers bra. I spoke to her to find out if there was any more information she had to share about this process, and she said the band still fits the same after removing the wires.
She also said that she had previously tried wire-free bras but found that the cups were too close together, and the Feathers bra was a better fit for her shape. If, like her (and me), your breasts are shallow and wide-set and you don't need much support, you might actually prefer how your bras fit without underwires. It's certainly worth a try in the name of comfort.
You may notice a bit of a flattening effect, because the wires help maintain the structure and volume of the bra cups. Without the wires and assuming you have the proper band size, the cups will be pulled outwards when you fasten the bra in back. If you have very narrow and/or close-set breasts, you might find that without the wires, your bra cups extend too far on the outer sides and there isn't enough volume at the center of the bra. As a result, the center gore may not tack, which means it's not an ideal fit. You can try a larger cup size to compensate for this.
It's always best to hand-wash your bras, but with the wires removed, you'll want to make sure the edges of the holes don't stretch or fray (unless you decide to stitch them), so don't put your de-wired bras in the washing machine. Hand-washing in a gentle detergent should help make sure they stay in good shape longer.