I would definitely sell yourself on your EKG ability. Alot of patients in the ICU have some kind of heart problem. Being able to recognize EKg changes are an important skill of an ICU nurse. Since there are a lot of comorbidities associated with heart problems, you probably have some good experience already. The move to ICU is a big jump though. There is alot of titrating of drips, something you are not used to doing on the floor. Just show that you are a competent nurse who is familiar with disease processes, and you should be alright. The only thing that I would kind of study up on is Vents and Resp stuff (ARDS/ALI, pneumonias, COPD exacerbations).
The ICU is a very rewarding place to work. You get a sense of actually helping people, instead of just carrying out MDs orders. You also get the oppurtunity to learn a gold mine of information and see things that you have probably never even heard of. good luck to you, I think it would be a good move.