For reviews: nothing detailed or comprehensive will come out right now, simply minor accounts/excerpts from new owners (i think--i might be wrong), b/c its a fairly new notebook. Do the google thing and see what you find.
<As the specs. are the same can I trust that the 1681 will perform like 2012? Will it be as silent?>
This new redesigned (Folio) chasis took at least a year and half to two years to implement--according to acer. It not only improves aesthetics dramtically but also positively addresses/improves ergonomic, build-quality, and upgrading flaws that are issues on their previous models--2012 included. This I suppose should also include better thermal/ventilation (not that their aspire series gets hot at all) design to enable much quieter performance--yet to be confirmed though! All in all, the new design not just looks good but addresses a ton of minor annoyances that plague notebooks, from upgradability and heat to sound and build--1.5 Yrs in the making is no quick fix!
<Will the screen be as good?>
Check out (bitbillyt) post on page 2, this should be helpfull--it lists positives and negs. and screen quality is one.
<In other words, is the battery-performace the only big difference (besides the folio design, which I am also exciting to hear peoples views on).>
YES, battery life is the only tradeoff--if you're confortable w/ that (1.5-2.5hrs) then it's no biggy. The new Folio concept provides killer looks: YOU WILL GET MORE HEAD TURNS ON THIS ONE!!! As far as 8-cell price and its avaliability, i can only guess it'll be somewhere between $70 to $100+, soon to be if not already avaliable from Acer (the 4500 & 4000 series use the same battery but theirs has more cells)--am sure, but don't quote me on this.
Hope that helps...