I had a really bad experience with Razer products.
They are small, flat, doesn't fit into your hand unless you lay your hand flat, which is not ergonic. Extremely sensetive buttons, so you had to hold back your fingers which leads to strain in the hand. The shape of the buttons on almost all their products doesn't let you rest your fingers in the side. You have to have atleast three fingers on the mouse with your thumb and your little finger on the sides. I can't hold a mouse like that. But I guess it's ok if you lay your hand flat, vertically on the mouse.
I tried to get used to it, but after a day it broke and I got really frustrated.
Never again Razer...
It's hard to find a decent mouse if you hold your hand in a natural grab on the mouse like I do. Even Logitech mouse have the same problem.
So I took a gamble and bought a Corsair M90. Mostly because it looked like I could rest both my ring finger and my little finger on the side. The mouse is very heavy though. But its solid and I am actually happy with it. Took some time getting used to the buttons on the side though. Most importantly it fits inside my palm so I can relax my hand while using it.
Out of the four mouse mentioned earlier I'd try the SteelSeries Sensei too, I just think its a very small mouse.
The Mionox might be a good second choice if you don't mind the shape.
I hope you'll be happy with your new pointing device!