It is hard to describe. I always found it kind of...I hate to say bland, because that has a negative connotaion, neutral. I think that's why I've seen it used in so many blends; you can flavor it with whatever you want.
From Rishi I've tried the blueberry rooibos, good, a mint rooibos, better, and a 'jamiaican red bush' that has lemongrass, schizandra berries, hibiscus, and a few other ingredients, best.
Republic of Tea has a new line of Be Well red teas that sell pretty well at my store, but I haven't tried them.