I think the posion scene probably could have been cut......but, why cut it? It does serve a purpose, and I think cutting it JUST to cut it.....I dunno, seems kinda wrong to me. I thought it added to how much Bond had gone through, and just how low Le Chiffre would go to win (desperation was really really seeping through).
For me, the poison scene was sort of like the staircase scene. I mean, yeah....sure, technically speaking the staircase scene could have been cut out completely. But, why? Ya know?
I think the length thing is just a moaning and groaning coming from audiences and critics who are probably conditioned for a 1 hour and 20 min film.