First of all, I would caution you not to look at ICU as an "up-grade" because you will soon see that though it entails a distinct set of nursing skills and abilities, your basic good nursing assessment
and skills are what is at the core of what you will be doing. It is best not to see yourself going to a "better" area, because, believe me, it will make you humble real fast. There are strong and weak nurses everywhere and just because a nurse works in the ICU does not make them superior. I know that is not what you said, but I had to address that!
ICU nursing is just that, a specialized set of skills and abilities, once I understood that, working in the ICU became a lot easier for me. As soon as the patient no longer needed those particular nursing skills and assessments, they were transferred off to another unit. Hemodynamic lines and drips, Vent management and sedation, insulin drips, lumbar drains and ventrics....end stage organ failure managament etc. etc. etc.
Personally, I knew I eventually wanted to work in the ICU when I was in nursing school, but I did a lot of other areas on the way. I would highly encourage you to go for it, but if it turns out not to be for you, don't feel like you failed, because you certainly did not. We need strong nurses everywhere. Follow your heart and that inner voice and you will make the right choice for you!