Given the unknown pedigree of the DC-DC switching regulator module specified in the question, it is difficult to speculate on whether the device would work well, work for a while, or fail outright. You won't know till you try.
The product description in the listing does specify a 3 Ampere capacity, so it should be good for at least a third of that, if it doesn't suffer from infant mortality, i.e. product failure at first power-on, as some poorly engineered or constructed devices, or even excellent and normally reliable products, do.
Also, as the question does not specify which model of the Raspberry Pi is involved, the following information from the Pi site might be useful:
Model B owners using networking and high-current USB peripherals will require a supply which can source 700 mA (many phone chargers meet this requirement).
Model A owners with powered USB devices will be able to get away with a much lower current capacity (300 mA feels like a reasonable safety margin).
Please note that, as with much of the "technical" information made available by the foundation, there is no specified maximum limit of power consumption, just a somewhat vague "feels like a reasonable safety margin".
A phrase like that should be grounds for worry.