Currently 6-0 in this mode-I think people should more or less ignore CS in this mode and just worry about roaming, getting kills, and taking towers. The reality is that in such a high-risk, high-reward format, there is no possible way you can get ahead by winning your lane in the traditional sense.
It kind of depends. I faced a Sona mid in URF mode as Cho'Gath and kept the creep line at her outer tower pretty much the whole time that she had one, and on top of warding river and building up feast stacks off of wraiths, that's really just about the most that can happen in that matchup. Sustain champions are certainly not worthless here, and you set them up in positions/matchups where they function best -- using some critical thinking. LeBlanc is pretty mighty in this mode, and with her in a game things will obviously happen really fast, but that's nowhere near the only flow the mode can take, especially considering each team gets 3 bans and blind pick.