Water! Wood and water are enemies, so a wood counter top next to a sink is a trap for moisture and mold, fungus and eventually, rot. The right type of wood can slow these effects...Teak, Brazilian Cherry,
mahogany...but any wood will eventually exhibit them. And then you have to factor in the general toxicity of the wood. One of my carpenters is highly allergic to the toxins in these types of wood. The toxins are what preserve them. Keep the wood away from the sink and the splash and it should be fine. There are schemes we use to mitigate the problems. Sectional cutting boards that abut a sink, yet are removable for cleaning, drying and maintenance...and replacement. On a recent trip to the SF Design Center I saw many exotic hardwood kitchen counter tops in the showrooms....those are showrooms! Not the real world! There was no water plumbed to the sinks....

I recommend most anything besides wood at the sink...with wood anywhere else you choose. One of my dream kitchen ideas has always been one of those giant antique butcher blocks, all wavy from the cleavers and butcher's knives, giant turned legs as an isalnd...far from the sink! Oh, and using the wood counter top as a cutting board will do just that. You'll wear it down eventually cutting into it with knives.

You asked for the cons and I agree with Ironwood. 1) Water where water occurs for all the reasons iron wood states. 2) wear/maintenance. Having said that I don't think that a fine marble counter top would require any less care. 3) Not mentioned very often, is sun. Sun over time can and will do as much damage as water.

I'm a woody so I can't let this go without giving you the most important pro of a wood counter top and that is it's beauty :)

I am looking at a kitchen remodel and am thinking to use wood top for the island, and another more durable surface for the main countertops since we are heavy into using our kitchen.

Wood can be done, but they are high maintenance and are easily discoloured by heat! Ironwood is right!

Wood = resealing every 3-6 months with oil. Only certain forms of cleaner can be used and they are never considered "clean" (if you use the medical definition of clean...which I do). Water left on the wood can/will eventually cause discolouration.

If you are a heavy user of your kitchen, your maintenance of the surface will be in the 3 month range. The oils smell horrible (even today's oil seals have plenty of smell). You will need to leave the counter top alone while the oil soaks in.

I guess the question becomes...how much effort do you want for a wood counter top? This effort costs time and money and loss of 'use of space" while the maintenance program is being implemented.

There is a reason why health regulations outlawed the use of wood in professional kitchens.