Is that Lahar a soft tail? Trouble with soft tail designs like that is that you cant control the direction of the flex ie. side to side as well as up and down. Just like this stupid old Ibis bow ti. I know its not a dh bike.... Pimp as hell ti frame but you can hold the bike between your legs and twist the front end almost 30 degrees in each direction.
http://kr.blog.yahoo.com/pyrosis02/959093
I rode one of those Lahars for a few hours, and from memory it was fairly stiff. The area behind the BB was massive, same with the stays.
You can control the side to side at the axle quite well, by having wide stays, they're stiff sideways. But yes, a triangulated design obviously has bennefits design wise. As you can control the wheels from twisting better. But it's not comparable to the Ti Ibis you mentioned or how it flexed, as you can obviously see where the Ti frame would flex through the whole frame. The Lahars mainframe I'd say would be as stiff as any bike of it's weight, and as stiff as most ally DH bikes mainframes.
Some cool old bangers coming out here.
What are the quick release levers I see at the tiop of the bushIdo forks Elvis? Scary. Or is it a shifter?