With Doom Legacy it's invincible. Especially with 3dfx glide or opengl. Graphics are ok. They kick butt on opengl using Doom Legacy. Sound kicks butt.
Music kicks even more butt.
I am actually working through this title with a friend via coop modem play. The only problem so far is that the game doesn't seem to work well with his newer modems and sound cards. We are working on this compatibilty problem to limited success. Despite this minor setback, we are both looking forward to playing at some point so that our long running Doom modem-gaming won't fade. I think it is one of the best games I've ever played.