I used that pump with an ex quite a few times and the results were amazing; both visually for me and in terms of increased pleasure for her. I think it took a while for her to get used to it so she didn't have it on long the first time but after a slow build up she was able to fill the pump and keep it on for quite a while. Obviously the results will differ for everyone and some may find it too uncomfortable to use at all.
Try searching the forums as there have been loads of pussy-pump threads in the past. Also check out the reviews for the product to get an idea of what people think of it. Personally I wouldn't hesitate in buying the Doc Johnson pump again if my current girlfriend expressed an interest in trying pumping