Definitely a properly placed sink and a trash pullout. Room for knives and cutting boards. Something to deal with compost would be nice. The rest depends on your layout. Mine is also close to my ovens and baking/mixer counter, so it has room for some baking tools, and has an overhang for younger helpers to sit for longer projects, like dealing with garden harvest, a box of apples that need to be made into pie filling, etc.

I'm not into mini refrigeration because of how much it costs for the room you get.

The most important thing is plenty of wide open, one-level workspace countertop...and at 33" rather than the standard 36". That lower height works best for us for chopping, kneading, rolling, mixing, etc.

--"The most important thing is plenty of wide open, one-level workspace countertop."

Very well said. *clap*clap*clap*

Undersized sinks and fridges are troublesome, ostentatious baubles. If you actually want to cook, you need a clean, clear work surface. Otherwise, an island is simply an obstacle that turns your work triangle into a bloated polygon.

Proper countertop height is the especially important as well as room to work and a place to off-load the messy dishes, scraps, etc. For me, location within easy reach of the cooktop is also essential and I consider the prep-cook zone more important than the old concept of a work triangle.

In addition to what rhome listed above, I like having room for and easy access to all my prep utensils, in addition to my knives. This includes colanders, garlic press, peelers, graters, choppers, etc.

I divided up all my utensils and gadgets into prep, cooking, and serving categories and stored them accordingly. I was amazed at how many prep gadgets I had, and I like being able to find them without having to dig through spatulas and salad tongs, which are now stored elsewhere.

I'll add a swing arm to clear cats and clutter right off the surface into a waiting appropriate receptacle. Realistically though, efficient lighting (as well as everything listed above)is mandatory in my opinion

For me, the ultimate work station had to have an extra sink. I have a small sink and it is not redundant or impractical. I keep my vegetable brush and cutting board right next to it. I use it for all my produce. Right next to is is the trash chute, which takes waste straight into the receptable below. It is really a pleasure to be able to process fresh foods so efficiently.
Here is one thing that I wish I'd thought of before...before the kitchen was fully functioning again, I started sticking the can opener and plastic wrap in the spaces that were to become wine storage. It sounds silly, but I loved being able to pull out the plastic wrap and can opener from those open cubbies. Had I known how handy it would be, I would have put in a second rack of similarly sized cubbies for the wraps. Mine are all in a drawer, which works fine, but not nearly as handy as the wine slot.
Also wish I would have been able to afford a cat & clutter swing arm. Could use one in my desk area.

Thanks for all of the great ideas! I agree that a sink is a good idea as well as access to knives, cutting boards, utensils, collanders, salad spinner, peelers, graters, etc. I use my knives, sink, and a cutting board most of all.

I haul out a cutting board at every meal and I'm trying to come up with a clever/attractive way to store them.

Oh, Country, what kind of receptacles does one brush cats into?? (ROTFL!!)

I'm on the other side of the "mini fridge" argument. I have a small fridge (bar size) from my old work storeroom which I first plugged in here for sodas for a party, and which has remained as a great place to store pre-prep vegetables, meat for parties, or large leftovers. The one thing I wanted for my new kitchen "just because I want it" is fridge drawers in the prep area, mostly for veg. It's not in yet, so I don't know if I'll love it as much I think I will, but oooh, boy! What a joy! Worth the money to me. It also solves the problem of distance from stove to fridge--I can put leftover wine, butter, etc., in the lower drawer and have them handy for unplanned needs (no little helpers to fetch for me).

Because the island is wider than the drawers I'm also getting a pullout with dividers for baking boards which runs behind it. Because it's nearly as tall as the counter I can put truly large boards in it.

And to be contrary, again, my island is going to be a little above counter height, at a comfortable level for chopping and shaping. I've ended up without a rolling area, but decided I could stand on a box for that. :) Whereas, since it's a small island (5'), the sink is going to be minimal. Really just enough for washing vegetables and brushing flour into.

Of course, all this is theory, as opposed to the experience that others have, but it's my ultimate island.