An excellent effort, Nick! You asked foor brutal criticism, so here goes:
1. No, it isn't over-weathered--looks real good.
2. As noted, the tracks are backwards. If they are vinyl bands, you can probably peel them off and turn them around. That said, however, there are numerous pictures showing vehicles with at least one track on backwards so don't sweat it too much.
3. The spare track: Add some rust to the end connectors and I think you'll be pleased at how it looks.
4. Spare track, part 2: How is it supposed to be secured to the vehicle? Tack-welded, on posts? Forgive me, but it looks like it has no visible means of support. I'm wrestling with this dilemma myself on my Firefly projects; not sure how to attach the stuff so it looks like it has weight to it and suport to hold it in position.
5. Commander's cupola: Try adding some gloss black to pick out the vision slots. I also note that there is no periscope installed in the housing on the hatch. Is that one of the missing parts? :-) Also, I see in the hatch the "dimples" from the ejector pins. Not a big deal, and easy to sand out. Or make a pad from a blob of epoxy putty and cover it up.
How about some more details, Nick? Whose kit, builder's impressions, gripes, etc.? And again, it really looks beautiful so please don't misconstrue my points above. Your model shows obvious attention to assembly detail and solid paint, decal, and weathering work. Two thumbs up!
Greg