Amazon Prime has shifted my buying habits to where I go there first for even small things like personal care items I would have otherwise bought at, say, Target.
I used to travel 4 days every week and so my weekends at home became extremely precious time. By buying that stuff on Amazon on Wednesdays from my hotel room, the free two day shipping meant it'd be delivered when I was working from home on Fridays. I was able to do the things I wanted to do on the weekend rather than spending time at the store doing what I needed to do.
I don't have that horrible travel schedule anymore but I still appreciate how I can just order shampoo from my mobile phone when I realize I'm running low.
I had Amazon Prime for two years and I ended up buying so much stuff due to the convenience and lack of "delivery cost shock" that I didn't renew it last year! No, I don't teach Self Discipline 101 ;-)