I've been searching for ages for something that would treat them. I used to use the old Clinique Pore Refining cream, which came in a lilac tube.
Sadly, after using it for months, I found it hadn't done anything except discolour my skin slightly, making it lighter than the rest of the skin where the product hadn't been applied, so I stopped using it. I eventually found a cosmetic solution from Benefit, their Porefessional (will do a separate review for that).
Then while windowshopping recently I saw Clinique had discontinued their previous lilac-packaged serum - it had more of a lotion consistency so I don't really count it as a serum... - in favour of the gel-cream green-packaged new version.
I immediately decided when I had enough money to spare for it that I'd get it. Everyone has been telling me pores become worse when you get older - especially my mother, for whom pores are also a concern.
And I have to admit, even though I was doubtful, it's true that the pores do look smaller. Blackheads are removed, there's not nearly as much dead skin collected there which I used to get, despite washing my face thoroughly twice a day.
The downside - the serum makes my skin so smooth that it feels greasy. I can't use it under make up, and if I use it when I'm wearing glasses I get frustrated at just how much more my glasses slide down my nose. It's rather annoying. On days when I'm going to be wearing make up, I just use it at night after my nighttime washing routine.
And of course the other downside is the price of it. However I've found you only need to use the tiniest amount of it to thoroughly cover the problem areas, so hopefully it'll last for a long time (I think I've been using it for about a month or just over a month now)
But, the important point, the pores are smaller.
Verdict: 7/10. (lost one point for the price, two points for the super slippery feeling)