WCA – I just answered on the other thread 🙂
They are primarily for comfort for me – I get a lot of hand pain.
At the moderate speeds I manage they are fine for cornering – perhaps better than risers. they are poor for control in the air – your elbows tend to go in and down and get locked into your sides making controlling the attitude hard.
maybe you tend to shift your weight further back as well.
so for rambling by bike – great. for more technical stuff / jumping maybe not so great. They do take a bit of getting used to tho
I have put conventional risers on teh bike now – but am seriously considering getting another set of mary bars for it – I have the marys on my commuter now.