I know I've mentioned it a couple of times, but I get zero "woohoo" from kratom. I've played with dosing quite a bit trying to find the elusive "euphoria" people talk about, but nada. The very most I get is when I microdose yellow or white through the day and by the time 3pm rolls around, I have a "let's get shit done" mentality. Don't get me wrong, white/yellow with my morning coffee is now my go to and provides a definite focus and mental clarity. But it's no party. And kratom definitely helped me kick booze to the curb. In two months, there was only one time I really felt the urge to drink.
As far as sides, I have experienced the headache/nausea and have found that microdosing keeps me from getting that. I'm talking 1g mixed in with whatever I'm drinking. As soon as I start to get any slight hint of a headache, I back off and drink a glass of water, and it's gone. Since it's often described as "eye wobble" I half wonder if meclizine would head off the headache/nausea. Not that I would recommend doing that so a person could abuse kratom, but just for the "oops, I took too much and feel like shit now."
The other biggest side is see is constipation. Taking fiber with kratom, problem solved.
Grapefruit juice and an empty stomach definitely improves kratom's effects. Thanks to OD for that hint.
There's a lot more I'm leaving out, but will leave others a chance to chime in.