I am a newbie poster here also, but have used the board for extensive research and have gained valuable insight from all the great people here. I just wanted to do what I could to "give something back" and share my experience with Clen.
I have done 2 full cycles and maybe one half of a third. The biggest difference I saw in my physical appearance was that I was definitely much more defined. I loved how my muscles looked "cut". I probably dropped 5-7 pounds, but felt like I built more muscle in the process. The side effects that were most prominent for me were nausea and a bit of shakes. I was completely turned off by food, so my diet was probably far too few calories while on a cycle which probably slowed my metabolism and made any rebound effect during the off cycle that much worse. I also became so nauseas during and after exercise, I felt like I was going to puke. My routine is 45 minutes weights/stretching and 45 minute cardio 4 x week. However crazy it is, though, I kept taking it. I think I have a love/hate relationship with Clen.
I don't necessarily do an ECA stack, but take a mini-Ephedra (before they were recently banned again, 10mg was available for sale and I stocked up) each morning both during Clen cycles and non-cycles. If I don't take it with the Clen, I tend to be more hungry. I am nowhere near 10% BF (I wish!). I am 5'3" 130lbs and am either a very healthy eater or a really terrible one. Usually there is no in between for me.
Anyway, not really sure where I'm going with this other than to say I'm probably going to go on another cycle next week.