Well, dump on it all you want
(not like you need anyone's permission to do so
).
I think this is a great start and a very admirable endeavor on Google's part.
Sure, like any mapping program, it's nowhere remotely near perfect. Ummm, maybe that's why it's a beta release?
What it does that I think is really good is that it shows were off-street bike paths are located. This is something that many mapping programs simply don't do.
Many of my own tried & true bike routes don't show up, especially the ones that involve hills or narrow roads or roads with moderately heavy traffic. This makes sense to me, since the biking directions are more aimed towards novice or occasional cyclists.
There are going to be routing glitches (it's beta, remember) -- hopefully people will have enough sense to not take the directions as a guaranteed sure thing, but to use them as a planning guide. OK, maybe I'm underestimating the gullibility of the average person here.

Maybe Google should overlay the directions with a big "beta" stamp with lots of "use at your own risk" labels. And if you don't like it, ignore it.
Call me a dorky optimist, but I for one am not going to dump on it on day one and throw up my hands and exclaim "why bother?"