PCU to ICU

I am a semi-new nurse. I have been working as an RN for a year and a half on a very busy PCU at a level 1 trauma hospital. We deal with a wide assortment of patients. Fresh strokes, MIs, fresh angioplasties, gtts, multi-trauma, lots of head patients (TBIs, etc), a majority of our patients are trached....just about anything goes on our floor. They are even considering adding stable vent patients. The ratio is 4:1 on a good night. It has been great experience, but I think I'm ready for something else. I love neuro patients and there is an opening on the neuro ICU. So, to finally get to my question........ how big of a transition will it be? I need some advice from ICU nurses who have also worked on a step-down unit. What changes should I expect (besides vents and nurse to patient ratio)? Any advice/words of wisdom would be greatly appreciated!