Yeah, this is a tough one for "regular users" to look for, since the console/system log look like so much gobbledegook, and it's not even clear what drive it's referring to.
SuperDuper! will generally (consciously & conservatively) fail if we encounter an I/O error during backup, and I'll help them determine whether or not the drive is in failure.
S.M.A.R.T. is, indeed, not a panacea, but it works pretty well for certain types of physical error (like slow spin-up due to motor and bearing failure, etc). Better to have it than to not have it!