Before I went to a larger skimmer in recent months, I ran a CSS clone on my tank. Exact make, just a different name. All the same, it did well on a 90g/30g sump. To make it even better, I bought a cheap air pump and dropped a stone in the skimmer body (drilled a hole in the lid and just dropped the air line down the main skimmer neck). That nearly doubled my output of skimmate immediately. Made clean-up a little more messy as I had to drag the stone through the dirty neck to remove it, but worth the trouble for sure. $15 upgrade that made a heck of a difference.
In all, they are not a bad purchase and I would say that there are more people using them than will admit. There seems to be an idea that more expensive is better, but that is not always true.
If you need intense skimming for an all-
sps tank, then the CSS might not do the trick you need it to. For general skimming though, it is just the right price.