For it to work as well as the Apple included charger it would have to have an output of 2a (or 2000ma in case it is written like that). If the max output is 1a, and if you have it split in two, most likey it would be 500ma x2. Even if you only plug one in and each port has a max of 1000ma when the other port isn't being used, that's only HALF as effective as the iPad charger.
The problem is the iGo website doesn't list the output in amps, and you can't convert Watts to Amps unless you know more information which they don't provide.
So if you can look on the charger or tell us how many amps it outputs, I could give you a better answer.
Bottom line: if it outputs 2A, you are good to go...however, if you split the output with another device, then you are NOT good to go. Or at the very least it would charge a hell of a lot slower than the iPad included charger. And if the second device is something that requires a lot of power (for example, the Moto Droid comes with an 850ma charger), it could possibly not even work.