About a years ago, you reported a bug to the Debian BTS regarding XKB option grp:alt_shiht_toggle not cycling between layouts. Did you reproduce this problem recently? With Xorg/Etch? With latest xserver-xorg-core in unstable? Does the problem still matter, even after reading Denis' reply[1] to your initial report? If not, I will close this bug in the next weeks.
I have tried to reproduce it with the current X.org 7.1 in Debian, and the problem no longer seems to exist -- both the left-hand and right-hand Alt-Shift pairs cycle through the layouts. Thank you. Amit Gurdasani