Ahh the beauty of cheap knock-offs!
The Sigma version is not exactly the same as the original Clarisonic, it doesn't have a charger (instead it just uses AA batteries), it doesn't do the clever beeping to tell you when to move onto another area of your face, and I'm sure there are other differences. However it is basically the same thing, a spinning brush for deep down cleansing and exfoliation. It has 2 speed settings and comes with 3 different brush heads, soft, medium and hard, and a little case to keep it all in.
And the best thing, it's just $49!
For me I think it's just about right. The price is great so even if it doesn't make a huge difference to my skin it won't be too big a waste of money, I don't care about the lack of charger or other features and, feebly, most importantly: I love the way it looks! Lookit the pretty pink brush head and the lovely retro style box it comes in!
Sigma's international shipping prices seem a bit overpriced ($19 for just this :/ ) so I'll probably be annoying my American buddies for a CP :P