You're not wrong.
Went out the other day, phone fully charged at 8:30 and apart from a 5 min call and the phone connected to my car via bluetooth when I was in it, it was never used for anything and the phone had drained itself dead at about 7pm.
This morning I did a factory reset and have installed nothing but what needed updating and it's currently been on battery for 2:30 mins and it's at 80% with Android OS at 79% use, screen 16% use, mediaserver 3% (4 songs on Youtube) and cell standby 2%.
It's just not acceptable and bordering on unusable without a spare battery.
My battery started draining itself fairly quickly again, even though I was using JuiceDefender, would be at about 20-30% when I got home. However in my case I'd kept the screen on full brightness (just because it looks good). A couple of days ago I turned it down to 50% brightness and left it as that, been using the phone as much as usual (couple of phone calls, twitter, linked in, text messages etc.), by 7pm last night it was still on 80-90%. Until I started watching some video's on it, started draining fairly quickly then (about 20% by the time I went to bed at about midnight).
At the moment it's showing about 95% (battery is green apart from the pin), been off charge since about 7.30am, and I've used it for accessing this forum a few times, emails, twitter and linkedin throughout the morning. Seems the brightness makes a massive difference (though can't say it will be the same in your case as I don't know what you have your brightness set at).
EDIT: Just read your post again, missed the bit about "Android OS at 79%". Mine is actually 89% left on the battery, Android OS 40%, Screen 36%, Cell Standby 9%, Phone idle 6%, Tapatalk 4%, Internet 3%, Android System 2%, Google Services 2%.
EDIT 2: Still not plugged it in, now showing 64% battery, 13 hours after I unplugged it. Oddly though the battery indicator still looks like its at about 85-90%, barely moved from earlier.
One thing you could try that I read somewhere is cleaning the contacts of your battery with a cloth, apparently this should be done every few months to keep the battery in good condition. I did do that with mine last week so maybe that's why I'm getting improved battery life.