Since this thread has popped back up, I'll chime in again.
I eventually finished my capsules and am now on the powder from Nutricost. Taking 2 grams per day although I think I should go for 3 on hard days. For anyone new to this, I'll back up what others have said. You definitely need to mix the powder with something. On its own, it is rather harsh.
We have had bad weather this Spring but it's finally starting to turn warmer and less wet. I'm a fair-weather rider so I have only recently been hitting the road again. I've already done 3 metric centuries which is unheard of for me this early in the season. My speeds are down somewhat as we are having one of those years where the wind is blowing pretty much every day. Yesterday's ride (64.5 mi) had winds of 15-20 mph so riding was difficult but I still managed a respectable 17.4 mph average. I'll take it under those conditions. Overall, I still feel that the HMB is working. It has been years since I've done a metric this early in the season and now I've done 3. I'm also finding that most hills don't get me as winded as before. We'll see how it all goes this next weekend as the ride is a metric with 3200 feet of climbing. I know I can do it if I pace myself. I just hope the wind calms down.