Caffeine has a distinct flavor, bitterness.  Its noticeable when not masked by tons of creme and sugar.  The best part about tea is that it contains such a small amount of caffeine in the first place.

Coffee starbucks grande 320 mg

Coffee typical brewed 8oz 80 mg

Espresso starbucks single 75 mg

Cola 45 mg

Black Tea 40 mg

Oolong Tea 30 mg

Green Tea 20 mg

White Tea 15 mg

But this list doesn't tell the whole story.

When I drink tea, I "wash" the leaves first.  This means I pour hot water (temp varies based on tea type) and let it sit until the leaves begin to infuse flavor/color.  This liquid is then poured down the drain.  This process wakes the leaves and removes some of the caffeine and bitterness.  If you prefer a "decaffeinated" tea, you could just pour out the first well steeped cup as well.  The first cup contains a large portion of the caffeine.  The next four or so infusions will have full flavor but lack most of the caffeine.  Some chemicals in tea are believed to slow or inhibit the absorption of tea.  There are also many active chemicals in tea that have calming and relaxing properties.  An amino acid called Theanine may be responsible for stress reduction, increased cognition and have calming effects.  What is certain, is that Zen monks have used tea for centuries to still and focus the mind.  Decide for yourself, my personal experience is that I have never experienced a twitchy coffee buzz when I drink greens and oolongs.  Instead I feel a sense of calm and clarity.

In some studies, tea bags have been found to have almost twice as much caffeine.  This is largely due to the fact that tea bags use "dust", a finely ground cheap version of tea that is more intense because more surface area of the tea is exposed.  This results in a quicker, stronger infusion with almost no flavor remaining for additional infusions.  Such is the nature of highly "processed" products like bag tea, its the chicken nugget of the tea world.  Where parts are parts, and artificial chemical enhancements are fair game.

Most people don't realize, loose leaf doesn't cost more than bag tea (but it certainly can).  Its just not available at your grocery store.  I checked, a barely drinkable brand called Tazo will cost you about $6 for 20 bags.  Which works out to about 30 cents a cup (although you could probably steep it twice, maybe).  The alternative is purchasing tea from where it is appreciated a something closer to an artform than a product.  China, the birthplace of tea.  My preferred vendor is a ebaystore called Dragon tea house.  An example of an "exceptional" but economical loose leaf tea is an oolong called Tie Guan Yin(review), (don't get freaked out by the chinese names), it'll run you about $10 (at the time of this post).  But instead of 20 bags, you get 100grams (the smallest increment available at this site).  Figure about 2-4 grams per cup that gives you $10-$20 for 50 cups.  Which works out to about 20-40 cents per cup.  In this example the loose leaf tea is about as expensive as bag tea, but you could easily pay $30 for 100grams too.  However, the difference in quality is like comparing fresh farmers market spinach to canned grey spinach from 1937.  While this analogy will serve most, a more in depth description of the differences between bag and loose tea can be found here.

That said, I've spent close to thirty dollars on a 100grams before.  And yes, it is good stuff.  Is it 3x as good as the $10 stuff?... debatably, but its still only ~$1 a cup.  Starbucks is $3-$5 a cup. Another big difference is that I'll get 7 infusions off a quality oolong.  That'd bring my per cup down to 20 cents technically.

Actually that is an misnomer.  There is no such thing.  The word 'tea' is commonly thought of as a any stuff you soak in hot water to make a beverage.  However, tea refers only to the leaves of the camellia sinensis bush.  Anything else is called a tisane.  In many countries the word tea is legally restricted to only camellia sinensis leaves, but not in the U.S., we like things nice and confusing.

Most people know what you mean if you were to ask for herbal tea, but its still displays your ignorance on the subject to any that know better.  Not a big deal, just something to keep in mind.  It is a common misunderstanding.

Flavored teas are almost always chemically enhanced, mostly resulting in odd and in my opinion artificial tasting teas.  Typically these combinations either obscure the subtle complexities of tea or mask the flavors of an inferior tea.  An exception would be jasmine tea, which can be done naturally for a rather pleasing cup of tea.