I had a 5 month lay off from working out, where I lost around 9kg of muscle and gained just a bit of 'puppy fat'. I wanted to get rid of that and start getting that muscle back. Being a nutritionist, my day to day eating is great to be honest (not big headed!) and I do like to think I know a fair amount about working out (no way near perfect, but I have learned a lot!)
I did what it said on the tub - 'take two capsules 30-45 mins prior to exercise'. Reading some of the tweets, I was expecting a 'rush' kind of feeling, but I didn't get that. I could feel something, about 20 mins after taking them, I suppose it was like a feeling of energy. So I started my workout, and after about half an hour I could tell a difference from when I used to workout, I did have a bit more 'punch' in the workout. How much is down to semtex? I'm not sure, but considering it has a hefty whack of caffeine, you are going to feel more alert anyway. I do think its also a mental thing as well. This product has been advertised as a fat burner, gives you twice the amount of energy etc etc. So I think when people take the product, they start thinking they have more energy and can go for longer, which in turn makes them push that much harder in their workouts. Now, I'm not saying that this product is a load of garbage and its just people thinking they can push harder. I do believe this product helps with enabling you to push that little bit more, where usually you would just quit. Any product that hasn't got 'strange' or dangerous ingredients in them, and helps to get a better workout, I would recommend people to try them. End of the day, you won't know until you try, and as I just said, if there is no harsh, dangerous ingredients in them, then trying them won't hurt you.
So, overall, I didn't experience a 'rush' like I have read people tweet about, BUT everyone's body is different, but I did feel a bit of a 'kick', and I have been having pretty decent workouts. I have gained around 4kg (not fat!) in a short space of time.