This is good feedback--appreciate it. I have several things I need to buy. I will do a lot of comparison shopping before I decide if it's worth it to me. So far it's been mixed--some things are obviously over priced, but some things were the same or lower than Amazon--with the membership of course. I think one of the reasons I'm considering it is that since I'm new to all this, I like the idea of being able to actually pick up and look at the sewer hose package I'm about to purchase rather than just look at a picture on Amazon. That's kind of a stupid example, but you get the idea.
I'll probably do like I do when I'm Christmas shopping. See something on the shelf and think, "that looks like a good gift!" Immediately get on my Iphone and google the item to see if I can order it cheaper online.
ETA: The trip planner does sound interesting--I'm going to look in to this more.