Crash wise I find it's only when I redose for a third time and above that the crashes begin to get me.
MDMA and Methylone (not Mephedrone) when abused would leave me short of breath and bad tempered for the week following. Used correctly I've not noticed any of these things.
You are right though, a drug as euphoric as this is going to be highly serotonergic, I'm prepared to accept a day or two of the blues.
[EDIT]
And finally, torturedrainbow: why not write up a report of the 5-IAI you tried, it did occur to me that there might be some funny business going on in one of these labs (2 new Nichols chems? Previously unheard of ones) and that bag of yours, if it was extremely fine and it seems almost electrostatic and the clumps bound together but didn't affect the consistency then its very very similar (I only had 125mg to play with mind)
My 1g of 5-IAI will be here today, along with Xanax, Poppy Pods (I'm going to try to make cooked flake opium) and all manner of other postal wonders.