I had the opportunity to compare the LG 181 to:
Sony 10 and 80: the LG is much better than the sony 10 or 15 and very similar to Sony 80 or 85 except brightness which is the stong point of the LG
JVC HD350 : first of all on JVC the blacks are blacker it is a great experience if your room is dark, in that case I do recommend JVC, in the other way LG gives a much more natural,3D and bright image.
Planar 8150 : similar black level, a better sharpness and convergence = DLP
About the screen, I experienced White and grey with and without gain.
first : white screen gain 1.2 : it was definitively too bright
second : grey screen gain 0.8 : it was much better : blacker blacks, unfortunately the texture quality was poor : a lot of grains and small sequins
Third : white screen gain 1 : still too bright in full RGB mode
So I recommand a grey screen with 0.8 gain to get the best black level on LG
About Flexibility : very easy to place the LG in your room, even if zoom and vertical lens shift are manual.
Convergence : due to Lcos system it is not perfect, similar to Sony and JVC projector except there is no possibity to rectify the convergence in menu.