Outside of the typical Whedon-whores such as myself and your average geek made up of Babylon 5 fans, Star Trek fans, Farscape fans and others, it generally went unnoticed in the general public. Which got it canceled.
Choice of words can be important here. Firefly went less unnoticed
then it did unliked
, as in declining viewer share and all that jazz. We're talking about a series that had a fairly high profile release on Fox and had a reasonable ad campaign for it. But 'the general public' never really copped to the program for no doubt a multitude of interesting reasons, and hence, cancellation.
And frankly after seeing the first three episodes in airing order, as I did at the time they aired - can't blame for those folks at all.