Its a great experience. My first donation I was scared to death- kept expecting the elders to break the doors down and haul me off in cuffs. Then there was the scare that maybe something would go wrong and I'd bleed excessively, or get light headed, etc.
But with so many medical professionals in the room- any mishaps are highly unlikely. They have the procedure down pat. It just takes a little time.
And it feels great knowing that something you did will likely save someone's life in the next few weeks. A pre-me baby, someone in an accident, someone on the operating table. And it feels good because I know that my blood is clean- and they won't have to worry about some disease.