I've been take omeprazole for 6 months now for the awful peptic ulcer I was diagnosed with. I take 20mg twice a day and all my symptoms have subsided for the most part. No more sour stomachs or sore throats in the morning and my acid reflux is tolerable. I noticed if I only took it once a day, I would still feel my awful stomach pains. So now, I have to take it twice a day which is fine with me as long as I don't have to deal with that nagging dull pain in my stomach from the ulcer.
As far as side effects go, I have not experienced any dizziness, headaches, or depression. It's all been a very positive experience so far and omeprazole is doing it's job!