Mean Green Cougar Red has a good discussion of what bus rapid transit (BRT) is and isn't, and what its pros and cons are. The two main points:

1. The definition of "true" BRT is important. A lot of bus services that claim to be BRT really aren't. In a nutshell: if it doesn't have its own right-of-way, it's not really BRT.

2. BRT is not a fully-equivalent alternative to light rail transit (LRT). BRT promoters who try to pass BRT off as "rubber-tired light rail" are, at the very least, exaggerating.

And on a related note, you should also take a look at Robert Boyd's post on The Pros and Cons of Taking the Bus. Among other things, you can take pictures while riding, as he demonstrates.