Look at the gear charts posted by Hermes. Compare the lowest gear combination you use now with the lowest offered by a 50-34 compact double. If you could achieve the same gear inches with a compact double as your current triple, you should be good to go.

Here's my personal experience. I have used the standard 52-39 cranksets with 12/25 or 12/27 cassettes for years on my road bikes, and it is pretty hilly where I ride. For commuting, the gearing seemed kind of high because my route is very hilly and I'm carrying much heavier loads. So when I built up a new touring frame for commuting last winter, I decided to use a compact double 50-34 w/ 12/27 cassette. The compact crank has been great, and I wouldn't hesitate to go that route again on my other road bikes. However, for loaded touring, I am not yet sure if the compact crank will provide low enough gearing. I'll have to determine that through trial and error.