i just got off it.... i liked the krealkalyn (i took some extra krealk with it) and liked that it wasnt loaded with a bunch of stuff i had never heard of (just looking for caffeine, basically).
it was alright. i had just finished a 100 serving tub of white flood though, and didnt take a break before moving into SCX, which i think lowered its effectiveness.
however, after i started mixing about 1.5 scoops (~340mg caffeine) and consuming half pre-workout and half intra-workout i really liked it... my gripe was that i crashed halfway through my workout when taking 1+ scoop preworkout only..... i took it the way fast twitch is recommended to take and that really helped keep my energy up.
i recommend it for a non-prop blend, and for someone that doesnt want something filled with stims (like 1,3 dimeth). just make sure you save some to drink intra-workout to keep up the energy.