I've just released a mew version of the client. The only major new feature is that the shot aiming line will now go either green or red depending if there is a wall or other non-unit blocking the LOS. This should help give a better indication if the unit has a clear LOS for long shots.
I think that's mroe of a problem with smoke/gas. Technically the walls shouldn't be visible in smoke; maybe I might hide walls/everthing in smoke that's further away than one square?