Not too shabby there. However, I would like to comment about the "structure" of it.
What you must take into consideration when modeling something is while you are concentrating on the form of it, you must also consider the function of it as well.
The hydraulic pistons at the top are way too long and there are too many. Applying heavy or overbearing forces would easily snap those like a twig. Consider a shorter, more solid, single piston with a four-link attachment to the arms. Also, beef up the links above the shoulder wheels. Again, way too thin.
Think of it like this... The longer the metal, the less force it would take to break or bend it. Keep it short, solid, and strong.
Also, there are no hydraulic hoses I can see attached to any of the pistons. The cables you do have are hanging out of the rear end unprotected, just swaying in the breeze. Stick them tighter against the frame of the body.
Something I teach my students when taking on any project is to ask themselves one simple question... WHY?
Why am I modeling this? Why is that part built like that? Why does this (insert model here) function this way?
By asking yourself why and then coming up with all of the answers to the questions, you will have yourself a good looking, yet functional model.
Professor of Digital Arts
Digital Media Arts College
Boca Raton, Florida