I am a big fan of berocca tablets and definitely recommend them. I suffer from mouth ulcers when I'm run down and often have a couple of days when I can feel they are about to fully develop. The past couple of times I've felt they're about to develop, I've taken a berocca for a couple of days which has prevented them from appearing. I also use them if I can feel a cold brewing and again I find that they prevent my cold from completely establishing itself. I also find that they increase my ablity to concentrate for long periods of time. Of course, this may be a placebo effect but it's very helpful if you have a busy day ahead of you!
On the downside the capsules are very large and quite difficult to swallow. I have tried the dilutable capsules but I'm not keen on the taste so prefer the capsule form. Berocca is also expensive, about £10 for 30 capsules.
Best to buy them when they're on offer or at Boots with their 3 for 2 deal of vitamins! Still, they're worth the price if they help you to keep feeling healthy.