I have heard rave reviews about serum in general on another website and was wondering what your experiences are. I'm 32, sensitive combo skin, very fine lines around eyes but nothing I'm remotely concerned about. I drink lots of water, eat well, use spf30 every day, go running 2-3 times a week and walk quite a bit too, don't drink excessively, drink hardly any caffeine and eat a healthy diet generally. Very light smoker (2-3 fags a week)- I know I would be better off without them but hey... 
What do serums do for you and what would they be likely to do for me?
Recommendations of products very welcome, the more budget the better!
TIA