I regularly ate rhubarb while growing up...usually in strawberry rhubarb pie but also in some other pies; we'd grow it ourselves--it's very easy to grow. The leaves are poisonous but not terribly so (Wikipedia cites an article saying it would take 5kg to kill, even if consuming unusually toxic leaves). The root you also should not eat, although I think it can be used for medicinal purposes. Rhubarb itself has questionable chemicals in it so I would not recommend making it a staple of your diet!
Rhubarb stalks are very tangy and have a peculiar aroma that isn't really like anything else, but is perhaps vaguely fruity, in a bitter, aromatic sort of way...which is why they make a good addition to pie. Rhubarb cuts/contrasts with sweet flavors very well.
Rhubarb is a really strong and sour flavor, and usually is not good on its own...you need to blend it with something else and even then, you don't want to put too much of it in. Generally, rhubarb without sugar tastes pretty bad...I don't like putting sugar or honey in tea but I'd probably be tempted to if I tried a rhubarb tea.