@prim - aha! welcome to the wonderful world of weathering. You'll be buying pigments and oil paints in no time
As for crits, I reckon it's an good use of rust, but for added effect it could do with being more subtle. To do weathering well it helps a lot to really look at actual rusty stuff and see where the rust gathers. It should be consistent across the model, not just on random bits. Finally, maybe blend it into the background a smidge more (just a bit of smoodging with a damp brush around the edge of the applied area should do it, assuming it's a water based rust effect you're using). Also, you need to do some weathering on the wheels (sorry dont know technical term) inside the treads - they're too clean compared to the rest of the tank.
strong points are: the scrapes and damage on teh stars, the rust on the front left (as you look at it) of the tank and the mud sploodge on the front and treads.
Finally, imho, try using some slightly different shades of green on different parts of the tank. fuel cans, hatches and suchlike are handled and moved around daily, so will be more/less worn than the areas of tank around them. Likewise, sunlight will not bleach paint uniformly, so any hatch that has been recently repainted will be a different shade. you dont need to use a diff paint for this - just mix in a spot of bone or brown for a slight tint in the base colour. you can highlight and shade as for the main green without fiddling with highlight/shade paints. Assuming you highlight/shade at all (apologies if you did, but it's not clear in this pic).
OK. advice over. You did ask...
As for me, today I played skyrim and cooked my very first ever ribs. 2 racks of babyback ribs, to be precise. Absolutely as good as I'd hoped they would be. Bloody awesome, in fact, if I do say so meself. Last night I did a bit of work on the deathjack and watched more daredevil. I have to say, teh bloke that plays Kingpin is really, really good. I'm actually almost rooting for him, and certainly I find the scenes with him in them far more gripping than those where Daredevil is jumping around kung-fuing criminal types. Not that those scenes are bad - they're actually much better than most all other equivalents I've seen on TV, it's just that Kingpin bloke is really fricking good. Also, Ep 8, final scene - well played Kingpin, well played indeed. Didn't see that coming...