Weathering has various levels of intensity though... A simple "wash" can put a little grime into the right areas, and washes (in model-making) tend to highlight detail, and help to achieve a look of "depth". Pretty much EVERY model used in the saga had a wash on it, as EVERYTHING has some level of "shadow" to it. Washes, while a weathering tool for modelers, are also used to show depth, dimension, etc.
I'd prefer to see a light wash then on some of the ships... I'm not so into heavy weathering though.
For instance the "battle damaged" deco of the TIE Bomber is not very good quality at all... The ship's fantastic, but if they wanted something more battleworn I think a simple black wash, left on a little thicker, looks better. Same with Gunships, etc. Big giant spots of silver look bad... Wash looks realistic.
Looking at the Death Star, it's spotless on the interior, but the exterior is "grimey"... It's nowhere near pristine. The same applies to TIE Fighters. Look at the models closely and they're "worn". Not to the extent the Rebel fighters are with their replaced armor panels, streaks of blaster burns and such, but they're still in a wash. A good example of this being done right is the grey big-wing TIE Fighter (the 1st BW TIE they put out at TRU a while back). It's got a wash, it shows the ship has been used, but it lacks the heavy wear/tear Rebel fighters are shown to have in the movie...
The A-Wings are pretty good examples of HEAVY weathering, and while film accurate to existing models, they're also a little cookie cutter looking if you buy multiples. Takes customizing to make a good assortment ultimately.
The AT-AT's in ESB, AT-ST's in ROTJ, AT-TE's, etc., all look fairly used though... So I think at least a wash is good to show some use, but still have a well-maintained look to them.
Looking around at photos of current and past conflicts in the real world though, you can see that "used" look without it looking like it was beat to hell. The US military is strict about keeping their armor clean, but if you look through photos of Bradley's, Abrams, Stryker's, etc., you see how there's inevitable dust/dirt.
So my $.02 as it were, is washes are a good thing and help add depth/realism to a vehicle... They don't look "worn", or poorly kept, but rather just more realistic. Big heavy weathering though? Unless it's for a very specific ship/fighter (Luke's XW on Dagobah, one of the more distinct speeders on Hoth, etc.), then I think "less is more" should be the mantra.
Washes though, I'm totally ok with.