I've had MDMA, MDA, Methylone, 90%+ cocaine and Mephedrone. From all those mephedrone is most similar to cross breed between very pure cocaine and MDMA. Its like coca in that it gives a state very relaxing/almost sedative, very social, increased confidence, lasts about 2x the lenght of snorted coca). Its like MDMA in that the euphoria is much more similar to MDMA rather than coca, also the ego is softened like with MDMA where with coca it's hardened.
How it differs from MDMA is that there is no PRONOUNCED psychedelia. With MDMA you can definatley start to get psychedelic thoughts and brighter colours (with 1 normal dose) with an extra push (sometimes more forcefull depending on dose) but the psychedelia is without a doubt there. When me or my friends have had more than 500mg-1000mg (0.5g-1g) throughout a 24hr period both of us notice quite a bit as far as psychedelic visuals go, especially in the dark.
With that said mephedrone gives a euphoric high that isn't really like cocaine in the euphoria rather a bit more like MDMA since it DOES have a VERY slight psychedelic aspect to it (the same strenght psychedelic wise that high grade marijuana and hash would have).
What I like about mephedrone is that the high clean, short (1-2hrs), it takes about 5min-10min to come on and I have yet to feel a crash from mephedrone. I've crashed from 90%+ coke before, even from MDA and Methylone but never so far from mephedrone and mdma. The seratonin depletion isn't nearly as bad as MDMA but you can definatley notice it quite a bit. Also I haven't experienced the need to fiend for a next dose like I would with methylone.
What I don't like about mephedrone is that usually when using it people want to re-dose at least once more and redosing more than once tends to produce additional stimulation when coming down so you may find it takes longer than dosing once to fall asleep. Also when redosing you tend to loose whatever psychedelic aspects there are in mephedrone and tend to get the euphoria still and everything else except the euphoria isn't so much 'eye wiggle' kind of euphoria (best I can describe it).
Another thing I don't like about mephedrone is that it may be harmful to the kidneys. Also it may be harmful for a lot of organs and we still don't know anything about it really.
DO NOT SNORT MEPHEDRONE! It produces extreme sweats and its much 'harder' on the body.
Also the most i've done in a 4hr-5hr period was 600mg-700mg in doses of 200mg oral and whenever I did more than one 200mg dose I found that I would be awake quite a bit where with MDMA I could have gone to sleep rolling if I wanted to.