Wicked expensive to take a taxi to Reykjavik.

There are a couple companies that do bus service to every hotel in town, including the Hilton.

http://www.kefairport.is/english/transportation/buses/

SO much cheaper.

As an aside, we did the taxi our first time in Iceland. The taxi driver was the only Icelandic person we've met who did not speak English. So we started with both language fears and a way too expensive trip in to the city.