We made our temporary plywood countertop for the island the other night and attached the undermount sink to it. It sure is nice not having a pile of unusable cabinets in the middle of our kitchen anymore! We have some framed end panels for the island that I'll attach when we get done with the plumbing. They basically look exactly like the cabinet doors, and there will be two per side.
The island is massive. In fact, the whole kitchen really has a "workplace" kind of feel to it, which I really like. I can't wait to get our concrete countertops done so I can roll out some pizza crusts!
Last night we plumbed the sink and disposal drain for the island. I'm not sure if code requires separate p-traps, but I chose to do it anyway because it's far superior than using one. I also put a couple 45-degree fittings in place of a normal tailpiece so we don't have to worry about hearing water dripping into the trap.
Using the air admittance valve to vent the system eliminated a lot of pipe and really made for a clean installation.
Under the floor, I transitioned to 2" ABS using a rubber reducing sleeve. I added a couple long-turn fittings and a cleanout, and then connected the new pipe to the old sink drain pipe.
I'm going diving tonight, but I hope to hook up the water supply lines after that. I was going to use copper, but I have Shark Bite fittings and some PEX here, so I'll probably use that with some copper stub-outs to run the sink and dishwasher supply lines.
After that, I'll have to figure out how I'm going to get power to the island. =)