Anyone using Mediation, Help to find best one

Is anyone using Mediation here,
If yes, I would like to hear the views,
I heard that
Inmobi and may me mmedia provides mediation.

I am using admob but I am not willing to put all my eggs into one basket (as advised by many expert) so I look forward for your kind view/experience about mediation network.

I also used adwhirl before, but sadly it had acquired by admob few years back and now no more active.