I've got the same problem as dze_xon has over here. I got an i5 3570k @ 4.8 ghz and a gtx 780 and over 50 mbs upload speed. I range in the high 300 fps whilst streaming while averaging a ping of 8 and I still have some lagg. It's no fps lagg, nor some kind of delay caused by ping. It's more of a stutter. It ain't as fluent as it's supposed to be. I got a 144 hz monitor, and whilst streaming it feels like 60 hz.
At first I thought it would be because of high cpu usage, so I capped my framerate to 144 and downscaled from 720p@60 fps to 720p@30 fps and I still had the same stutter at only 70 percent cpu usage. It's very strange. I'd really like an answer for this aswell, so that's the main reason why I respond, instead of making a thread of my own.