Sperasoft is an outsource studio, so their main advantage is that they have good artists relatively cheap. If you are from west I doubt you'll find their salaries competitive.
I think noone will answer such questions because of NDA and lack of people who worked in such conditions. You should ask Sperasoft staff directly. They are indeed huge & legit, can't say about cool — didn't worked there. I think they are our biggest gamedev outsource company. First of all, do you speak russian? If not, you…