The only guy that is nice, good-natured and sincere is probably Dussardier, but he's simple and naive, somehow reminiscent of Charles Bovary though not very similar. And he's almost a minor character.
Update at 5.54pm:
Sénécal, as it turns out, is disgusting just like Deslauriers. Look at this passage about him, at Arnoux's factory (Sénécal= the deputy manager= the Republican):
"As soon as he set foot in the room, the deputy manager noticed a breach of the regulations [...] Sénécal told them that they would have to stay behind an extra hour. 'Serve you right', he said. They bent over their work without a murmur; but their anger could be guessed from the hoarse sound of their breathing. In any case they were anything but easy to manage, since they had all been dismissed from the big factory. The Republican governed them harshly. A man of theory, he respected only the masses and was merciless towards individuals".Oh the irony.