After a brief look into VOPs i've got a question - instead of stacking a lot of primitive nodes is it possible to write something like expression in VOPs? I mean are there any node with simple syntax analyzer that does some simple math operations?

The reason i'm asking it, is that i was needed to reflect a vector, and instead of simple 1-string expression i had to create like 10 or so nodes. I understand that VOPs is very fast, but i think it's also possible to make “Expression VOP” that is gonna be as fast as other VOP nodes?

That would be the Inline VOP node you are looking for.

Aha, nice, nice, thanks!
*digging in docs*

A mentoined by Erik, use the Inline VOP to inject custom vex code.

If you want to reflect a vector along another, use the Reflect VOP.

The attached file uses an Inline VOP to randomize v and then a second VOP SOP to reflect these random v vectors by the surface N normals.