Pros: Open design, overal pretty flat sound, lightweight, great sound, very moddable
Cons: Somewhat fragile, leaks sound (obviously), y-split cable isn't great, initially uncomfortable
I love my MS1i's, they sound amazin, after I got used to it are quite comfortable and just sound beautifully open. The sound is quite flat and in turn is quite good for an amateur music producer like me, my dad's an expert on mastering and such and he says my mixes sound quite good.
The cable has an y-split, which isn't too bad, but the cable itself after it splits is twisty and annoying and I had to replace it. But because the headphone is so moddable, it was really easy to do. For the price this headphone really is the bang for your buck, but be careful of import taxes. I had to pay about €25 extra (~$32) for importing it from America.
The headphone leaks sound, as you would expect. This is not a disadvantage for me as I only use it indoors in my room. But it's something to think about before buying it.