It finally annoyed be enough to start whining ;)

whenever I switch display (pure xrandr call) from laptop's LVDS
(1600x900) to external display (1920x1200) gkrellm and
xfce4-pannel, while maintaining horizontal position, jump up so their
bottoms gets aligned.

Here is how it looked originally:
http://www.onerussian.com/tmp/gkrellShoot_08-20-14_103547.png

and here how after the change of resolution
http://www.onerussian.com/tmp/gkrellShoot_08-20-14_103624.png

Going back from external bigger screen to smaller laptop -- seems to be
the same story (although I think I saw it not happening).

May be related:  another pain is to "dock" gkrellm window on the left so
that work area for automated windows layouting gets "contracted" a bit
more from originally reserved according to the width of the xfce4-pannel
which seems to be a few tens of pixels naroower than gkrellm window.
while I move gkrellm window from the left, awesome seems at some point
narrows working area but then expands it back to match the width of
xfce4 pannel.  At times I do manage to catch that golden spot but it is
"too tricky" ;)