From my experience, ask yourself this: how much free time do you have and how much of that time are you willing to spend price checking and waiting for the "right" time to buy in?

After spending lots of time waiting I decided buy in a while ago and I can tell you it is a wonderful feeling to not have to keep checking for the right time to buy. Whether it goes up or down, you are only investing what you can afford to lose (right?) so you can simply sit back and enjoy the ride.