I just finished using the Shark CarpetXpert in my living room and I must say, I was impressed.  The dust and dirt this machine picked up was amazing.  I have tried several different carpet cleaners before and Shark out cleans them all. 
I am giving a 4 out of 5 stars due to the size of the tanks.  Every 5 minutes I had to stop and empty the dirty water tank or refill the solution tank.  That is the only drawback to this cleaner.  When it comes to cleaning carpets, I give it a 5 out of 5 stars.