Deciding on the 40mm lens?

Aside from the obvious widest aperture differences, what are your feelings about the Canon 40mm lens when in discussion with also the 35mm and the 50mm lenses?  I'm still looking to purchase ONE prime lens, and the 40mm is smack-dab in the middle.  It also has good reviews, and inexpensive (opposed to the 50 1.4, and 35 2).

It's allegedly a good performer at it's wide open 2.8, whereas both others need to be stopped down to at least 2.8 or more, before becoming decent.

None of the 3 lenses in question have IS(I don't think).  So that's not an issue.

So what else should I be considering before making a decision here?  Thanks.