I can assure that with Conjuration of 82, Flame Antorachs are not merely "trainer summon." They're long-range fire damage; can svck up a lot of damage; are easily replaceable when needed; can target flying dragons and, they keep you nice and toasty in those cold caves and dungeons. Further, I like to cast them into new rooms to see if any enemies are in there.
I believe Ytheria was referring to the familiar as the "trainer summon," not flame atronachs.
I was a little surprised how squishy the familiar was. I understand it's not an atronach, but I think I casted it like 4 times and then never used it again. Flame atronachs available early enough to make it pretty useless. The Flaming Familiar is pretty win though, if not only for amusemant.