Almost but not quite as good as WBCL
To be fair, if I had started off with this brand of cat litter I'd probably be happy. It clumps effectively and while it does track (ALL litter tracks to a degree) it is relatively minimal to other brands I've seen. It also seems to control odour equally well. However, I started off with World's Best Cat Litter and was shopping around for a replacement because WBCL is awesome but costly. As a result I wasn't quite delighted and have reverted back to WBCL. First of all, it's a lot denser than the corn grain so more weight doesn't mean it takes up as much space. But really I had two major problems with its performance:
(1) stickiness - the clumps were not as neat as with WCBL, leaving sticky residue on the scoop, on the side of the litter box, and sometimes breaking up. I practically had to scrub my litter scoop with an old toothbrush to get rid of some of the clay, and similarly cleaning the slats on my overspill tray was not enjoyable. When it came to to change the litter box it was much messier than usual and because it's clay I couldn't just wash the remaining particles down the bathtub drain. This stickiness extended to finding small bits of clay stuck to the walls outside the (covered!) litter box and around the entrance.
(2) dust - it does track a little, really no more than WCBL, but the problem with the dust isn't the tracking. WBCL is relatively coarse, and the finer dust tends to settle to the bottom of the box. Extreme Classic is much finer all around and scooping my large litter box often felt like I was kicking up a cloud of dust that I had to try and not breathe in. By the time it came to change the litter box there was literally a fine film of dust on top of the box. It doesn't feel pleasant and if push comes to shove, I'd rather have corn dust than clay dust around the place.
Overall I found that litter box maintenance with Extreme Classic was just higher than with WBCL and while I am still looking to reduce costs, I am not sure I am happy with this particular trade off so I've gone back.