I have been following your thread for some time now and have thought of a couple critiques.
1. the seams where the rear bumper meets the rear quarter panel looks too soft compared to the front bumper and front quarter panel seam. at first, I thought this was just me but in each render, and from every angle, this sort of stuck out.
2. your lines have a definate square and hard angle theme to them but your door handle is the opposite. it is very round and looks out of place. I don't think many car designers would mix those types of looks.
3. even though you haven't merged the halves, the top of the front windshield looks too pointy. maybe it's just me?
4. the mirror looks to be an integral part of the door. What about making a piece that the mirror attaches to? Maybe a seam for a folding mirror like most production cars?
5. the piece that "connects" the two side windows would probably not be a continuous piece from the roof to the rear quarter. maybe try a nice seam on the top and bottom with a semi gloss or satin black shader.
just as a suggestion, why not try making the front blinker/reflector into the hard seam along the tire?
where is the antenna? will there be one?
The studio render is coming along nicely except it still looks a little dark and gives away that it is cg quickly. I very much like the design. You are making it much harder for us to critique. Keep us posted