We have hardwood floors (site-finished red oak) in our kitchen. Just built the house 5 years ago, had the builder put 4 coats of oil-based polyeurethane down. I wouldn't trade it for the world! I hate walking on tile, and think vinyl in a large room (e.g. a kitchen) looks terrible.
Friends of ours put Pergo in their kitchen when they built a couple of years ago - the floor looks as-new, but there's no depth to the material - it looks (to me) like plastic.
If I had it to do all over again, I wouldn't do anything different - there's nothing in my opinion that looks warmer in a kitchen than real wood.