Lots of good advice here, nursing staff is fluid, people change jobs all the time. It is an expectation, especially for new nurses to move around before they find their niche. Anyone who may be negative to you is probably stuck in their own rut and not willing to make a change.
I do have a couple of words of advice. No matter what - DO NOT join any discussions about the negatives of the job you are leaving, Any explaination to your peers can just be you are looking forward to a new opportunity and new learning experiences. Most likely you wil lhave an exit interview with a supervisor, so if you have any constructive critism this is the place to offer it - but this is not a gripe session, either; if must be constructive. It is also a good place to mention anyone especially good on your unit. kudos never hurt.
Best of luck in your new position.