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The answer to this one took a bit of research and now fills up a large chart that we've posted at https://www.lasvegasadvisor.com/hispeednet.cfm. It shows which casinos have it (out of 59 listed, 26 do and two will soon), which have them in the rooms or just in the business center or lobby kiosk, and how much it costs.
It's a very handy chart if you're traveling to Las Vegas on business and need to hook up (and the most it'll cost you is around $10 a day).