Slim - i got my Q Core SL in the mail today, and your review is dead on. I had the stuff sack/patch kit at 9/10ths of an oz, and pad/stuff sack at 21.4oz, so pad alone at 20.5oz. very close to your weights. i didn't measure length, but did check the width inflated and it comes to 19 inches as you said, not 20. if thy are saying 20, they have got to be counting the half inch seem on each end, which in my book doesnt count in the inflated measurement. you do fight air on the valve, but like you said it's pretty standard....not a deal breaker for me, but exped's system was pretty sweet.
the pad is pretty quiet when moving around, and i do agree it appears to be overall more durable than the synmat ul.
i like my exped alot, but it will most likely be going to the classifieds soon.