I'm not to keen on the Wookiee. It is an intersting use of parts but for some reason it doesn't really appeal to me. I think if you make the skirt/hat less recognizible an painted the Grievous parts, like CHEWIE said, it would help a lot. I'd ditch the AT-RT driver gun, that thing looks ridiculous. The black on the fr doesn't look very natural, try drybrushing it on to give it a more realistic look.
The 501st clone sets look pretty good. I like the little melted armor disk on the yoda version, it is a nice touch. Again I'm going to agree with CHEWIE, Hasbro gives us SA for a reason, use those joints.
You are off to a good start on your CW Obi-Wan. I took a similar route on mine I made awhile back, but I used a SA clone. Here's a pic of mine if you are interested:
I really like the vintage Saurin. He is a Saurin, not a Trandoshan BTW. They are close but not the same species.
I look forward to seeing another update from you soon.