I love the BBS Field Guide. Its keys are well thought out, if not entirely perfect. The species accounts are well put together and appear to contain all the information you would want for a thumbnail sketch of a species. I also love that it's online, although since using it online I have paid for an actual paper copy
However, sometimes the obvious inonsistencies drive me mental. Look at this one:
The text clearly indicates that for this species the leaf length is "2-2.5mm" long. On the other hand the image adjacent clearly shows the leaf as barely 1mm long. How am I supposed to know which is correct? Especally when I am trying to differentiate between two species where this would help enormously (B.gemmiferum and dochotomum). As it happens gemmiferum also has a divergence between text and image, though not as bad.
I had this with another species too, although I eventually had to pick which was correct based on the (potentially misidentified) plant I had in my hand. Who knows how many species this glaring error pertains to.