i tried it a little while ago, it was the first NO product i tried that actually did something for me, i had ridiculous pumps during my workout and for bit after it.
i used GB + WB, i had to change my workout because i usually work bi's + tri's during the same workout, but i had to change back to doing tri's with chest and bi's with back because it felt weird when my arms would be really pumped and id try to keep going with my workout but doing some arm exercises (pressdowns, overhead extensions, preacher curls) it felt like it was limiting my ROM on those exercises.
it felt great, id buy more but im not out of GB yet, i ran out of WB prematurely because a few of my caps (i counted 10) were broken (and 1 was broken and the stuff hadnt leaked out, but when i took it it tasted disgusting due to the hole in the cap) so i ran out earlier than i thought i would.
i got a 10% off coupon from bodybuilding.com forums, so that had a bit to do with my choosing it over other products, + everyone was always talking it up so i gave it a shot.
stacking them both was great, i couldnt afford ANY supplements for a long time and it completely messed up my workout, where i would have to wait a day or two after a workout i was able to get a workout in every day, taking mon + tues off, i attribute this mostly to GB though.