From my experience, when used in moderation it doesn't cause any of the negative effects typically described in trip reports. To me it seems that people overdose by ingesting several hundred seeds in one go without having a clue what they're dealing with. I took 3 seeds the first time I tried it, which was enough to get a taste of the effect for me, and then gradually increased the dose by a few seeds at a time over several weeks until I reached a point (around 50 seeds) where it was pulling so hard on my mind that I didn't feel like going further. I haven't noticed any lasting mental impacts.
Drinking a liter of vodka in one go without having any experience with alcohol also potentially causes extreme delirium and confusion, yet people drink alcohol all the time and are mostly fine.
A lot of ethanobotanists report that peoples using datura traditionally or spiritually (eg in the context of Ayurvedic medicine) don't tend to experience as many negative effects as people using it recreationally:
But with that said, I would strongly caution people not to take tropane deleriants. Unless you really know what you're doing, there's a solid chance you are going to end up being high for way too long or end up in the hospital.
I'll also caution codr7 that seeds (especially from different sources) can have hugely different potencies, so be careful dosing anything via seed, especially something as serious as datura. It sounds like this works for you, so I don't intend to sound patronizing: I just want to make sure that I am spreading harm reduction everywhere I go, and datura/tropane alkaloids can be very dangerous.
I am aware, it's not like there's a lack of warnings out there. But 3 seeds aren't going to cause a bad trip for anyone, no matter how potent they are. The bad trips are from ingesting 100-300 seeds without prior experience, which is a very stupid and risky thing to do.
Drinking a liter of vodka in one go without having any experience with alcohol also potentially causes extreme delirium and confusion, yet people drink alcohol all the time and are mostly fine.