I think that for the most part, this quantity limit is a compromise worked out in favor of just about everyone (except, perhaps, passengers). The airlines get fewer carryon bags but also fewer irate business travellers, and the airport vendors get more sales. The feds get to look a bit more reasonable, and TSO's don't have to deal with constantly weighing whether or not to ignore people who are trying to smuggle small quantities on their person.
I'm waiting to see if winter messes with idea of how much is reasonable with regard to food/drinks for young children. If you've read the Trib's famous "Camp O'Hare" story (which happened on a Sept day, actually), you know that passengers can end up stranded in terminals for well over 24 hours, and currently, airside merchants dealing in baby food/supplies are few and far between. (Any of you Chicagoland folks want to open a BRUS mini-mart at O'Hare?)
I think that this particular limit will stick, with perhaps some adjustments to accomodate duty-free purchases coming in from abroad. It will be interesting to see whether merchants decide to open new outlets in airports (both landside and airside) to take advantage. It will also be interesting to see how many municipalities pass new "street-pricing" ordinances that cover airports.
I'm not going to say I'm totally satisfied with the changes, but I can live with the new limits without undue hardship.