For an eloquent articulation of why one might choose a fast lens over a technically more competent but slower lens, see Dante Stella’s The Legend of Lux-Do. Goofy, yes. Tongue in cheek, definitely, but then fast lenses are not serious things.
Despite all the folderol about photo-journalists needing them to get that crucial shot, most photo-journalists I’ve known are far more comfortable using a flash. The chances of successfully shooting in low light are far higher with a flash, but fast lenses aren’t about succeeding on the same terms that we normally use to judge photographs. No, fast lenses are about hubris, plain and simple. They are about knowing you can walk into that dingy bar, take the darkest booth in the back, and still be able to get a picture.
Ultimately, fast lenses are fun. Fast lens that also happen to be cheap and small, like my new CV 35 F1.4 SC, are particularly fun, despite their limitations. If you are worried about distortion, light fall off, resolution or pretty much anything other than being able to say, “but this one goes to 1.4,” don’t bother. Nothing to see here. Move along. There are a plenty of well lit bars near the mall.