I picked up this little jar in my local The Body Shop store a few months ago because its promise of 'fighting dull, tired and grumpy skin' was irresistible. I knew that it would be handy in winter, when my dry skin would be at its, well, driest. So whip it out in winter I did, and it actually delivered. I'm actually still using it in spring, because it's just too good to stop using, I love how the citrusy smell reinvigorates me in the morning, and the texture is so soothing and cool on the skin. You might think that gel on dry skin wouldn't be as effective as a thick cream formula, but no, it's just as moisturising. Amazingly, it does provide a natural-looking glow when applied, but that won't last for too long in hot weather. I haven't noticed a long-term difference, but day-to-day? Definitely.
This is only one product in the sizeable Vitamin C range, and I'd definitely recommend that you have a look at the others.