I would place paper towels on the wire for the first couple of weeks, but I just put a bunch of 3 week old's on 1/2 hardware cloth and they're doing great. Barred Rocks, RIR & Sussex. They run around like it's solid ground. Took a couple days for them to get used to the wire, but there are no ill effects 5 days in. Took them a day or two to adjust, but they're fine now. No bleeding feet, no crippled legs. If anything, it's probably making their feet tougher, which can't be a bad thing.
The best thing about it... no mess! The paper towels & shavings were starting to be a real pain. Messy, stinky & always needing to be changed or turned. Mine is set up on 2x4 framing, so there's 4 inches between the ground and the wire. I was going to put it on legs, but opted to just sit it on the ground to reduce air drafts. I bought a cheap $7.00 plastic tarp at Lowe's & laid it directly on the shed floor, then set the brooder on top of the tarp. When I'm finished brooding, or if it needs to be changed sooner, I simply move the brooder, roll up the tarp & throw it in the trash can. The poo falls through the wire, 4 inches to the ground, stays dry, so the smell is reduced too.
Just my .02 & what's working for me...