I've been drinking green tea for several years. A few months ago, I wen through a period of being run down and as a result I switched a few things in my diet including cutting out caffeine (bar the odd glass of diet coke now and again). I usually drink around 3-4 cups a day and if I had to describe the taste, I'd say it tastes like a weak tea. Personally, I don't taste that much of a difference between decaffeinated and normal green tea though it does depend on the brand. I've tried a few brands over the years, with the nicest being twinings, clipper and tetley - tetley are often on offer in the supermarkets at 50 bags for £1 which is when I usually stock up!
Since upping my green tea intake to 3-4 cups daily, I've definitely seen some benefit - if I've had a cold it clears up in a few days whereas before it would linger for weeks. Green tea is packed with anti-oxidants which boosts the immune system. A few other noted benefits are linked with weight loss as green tea has been shown to boost metabolism, improving brain function and can aid against cancer, heart disease and cholesterol.
I've seen a few new 'flavours' of green tea recently - the gingerbread twinings version sounds really yummy though I think these have caffeine in.
Whats your favourite tea?