Harsh but effective. I used it in it it's oral and injectable form. Pretty much most people who have dabbled with steroids have used Clenbuterol at one point or another.
Sweating, shakes, cramps, twitches, and rapid heart beat were sides I had to dealt with. Anxiety was always a side effect that loomed on the horizon.
The trick with Clenbuterol is to start small and slowly work your way up to a comfortable dose.