If you expect to open the viv and put your hands in fairly frequently, for reasons other than feeding, your snake should not associate the opening with feeding. For example, I feed my hatchling every 5 days. I also open the viv at least every other day to provide fresh water, and every day (except for 48 hours after feeding) to take her out and handle her. She does not associate the opening with feeding. My adult has always been fed inside his tank, and is about the least aggressive snake you can imagine. I frequently take him out and handle him, or open the tank for fresh water.
On the other hand, if you don't expect to be opening the tank very often, you might want to feed outside the tank for the reason Simon mentioned.