In our last house we built, we had an island fan (electrolux) - it worked very well, but in the end, we didn't think it was worth the extra money (it was quite a premium compared to the same model in a wall-mounted version).

In the next house - we are trying to be more frugal with this one - we will put either the sink or nothing in the island, and get a power pack for a cabinet or a microwave/hood fan combo over the range.

@mediocore - as kitchen ventilation specialists, we would STRONGLY advise against using a microwave/hood combo. They're almost useless (100-400 CFM), too noisy (6 to 8 sones is not unheard-of), and cannot handle any decent amount of cooking (filters are too thin, get clogged too fast).

If you're looking for a budget solution, a "power pack" or "range hood insert" is definitely a much better way to go. Even a cheap - but full-size - insert, will provide much more ventilation power than any microhood.

Good information to know, hopefully you can find something that meets your needs and is within budget!