IMO, the State has done a better job presenting evidence that she was mentally ill, but not insane, at the time of the murders, than the Defense has done in trying to prove she was insane.
Personally, I'm not sure whether she was or wasn't. There's some things she did that make me lean toward insanity -- for instance, she forwarded the kids' grades to Parker, just minutes after shooting them -- it was like she was doing an ordinary, routine thing, like on autopilot, as her children's lifeblood was pooling on the floor. And...she said they were still making noises...well, they wouldn't have been...so what was she hearing? In her interview w/ police on 1/28 (and reading the transcripts) -- she appears to be drifting in and out of reality, and making odd statements (like the squeaking chair when asked if she understood her Miranda rights) that might indicate she was in a psychotic state. But, as Dr. Stein pointed out -- that could be due to being in shock and also the effects of her overdose of Lithium -- she probably WAS in a bit of a psychotic state at that point, but whether or not she was on the day before is the big question.
That's why I'd love to be able to read those journal entries in the days prior to and the day of the murder. I'm gleaning from the little tidbits we're getting here and there that she might have been drifting in and out of some sort of psychotic state (or was it an alcoholic haze?) -- perhaps her statement "I really have lost my mind" was when she was in more of a state of lucidity, reading some of her earlier entries that were totally out there.
The biggest problem is the 3 day waiting period (actually it was 5 days). If everything had happened in one day, that would be one thing. But...to wait that 5 days...that means she had to maintain this plan of killing herself and the kids over a period of time..that would mean she'd have had to remain in a psychotic state for at least 5 days, and that during those 5 days she'd either need to not understand what she was doing (which, clearly she was understanding), or hold the belief for 5 days straight that what she was doing wasn't wrong. And that's why the journal entries -- in the whole -- are so important.