I see no reason to make "solid" saves aside from when I switch to another character. Auto/Quick does it for me just fine.
I've had too many games, from too many publishers, lost completely (or many hours of progress lost) by just counting on a basic level of saving, to ever do that again when I've got the choice.
Standard practice for me, with Bethesda games, is to keep a rotating block of 10-15 manual saves - once I get up to that many saves on a character, I start saving over the oldest one. Plus I quicksave before entering new rooms/areas, after beating notable dudes in a dungeon, before doing anything risky, etc. I've basically never counted on Auto saves.... I even disable some of the triggers (like "save on wait").
These huge lists of saves that many of us make, is one of the big reasons there were constant threads over the last months, with people wondering if Bethesda would make a modern "folder/profile"-type save system like those found in Bioware and other companies' games - being able to select which character's saves we wanted to see would cut down a great deal on accidental overwrites between characters.
(Which leads to another thought - anyone who wants to play more than one character,
has to use manual saves - if you just use Auto & Quick, you'd delete your old character every time you started a new one.)