Many of the big named road bike companies tried to make mountain bikes in the '80s and '90s with varying success. The Colnago Master MTB is well regarded, though not particularly expensive in the resell market. I'm sure the Decor is a fine bike with shaped tubes and it looks like they got the geometry right. The kit is a bit underwhelming on yours from what I can see looks like Deore DX, but being Shimano, it most likely works fine...
Tend to agree. Had it been a steel frame it would have been far more desirable. Have you got additional pics / specs? Is that chainstay ripped up with chainsuck?
Rossin Concept MTB 1990 - Full XTR M900
Litespeed Ocoee Titanium MTB 1992 - Grafton / Bullseye / Syncros / XTR
LeMond Z Team Issue SLX 1991 - Full Corsa Record / Sigma
LeMond GAN Team Issue GLX 1993 - Full Dura Ace (7400)