To repond to thalp's question of Stevens' dignity: I found it ironic that, as thalp said, Stevens denied working for Lord Darlington. If anything, the more dignified thing would have been to defend his employer's honor, if he felt that Lord Darlington was worthy of it. It reminded me of how, earlier in the novel, Stevens Sr. "defended" his employer to the drunk men; becuase Stevens Sr. was new to the household and assumably knew little to nothing about his new employer, he really had no reason to consider his employer worthy of defending. I wonder if Stevens really finds Lord Darlington dignified or he feels it is his duty as a butler to at least pretend to find him so. So far, it seems as though we've seen few qualities in Lord Darlington that make him appear honorable.
I agree completely with jlam09 that Stevens is clearly using professional reasons as an excuse to see Miss Kenton; it seems convenient that the professional reasons to see her emerge just after her marriage has fallen apart. I don't know if Stevens will ever get past his inability to form relationships, even after being reunited with Miss Kenton.
Also, as thalp pointed out, Stevens does appear to have some feelings of regret. This seems to be one of the only clear emotions we have seen out of him thusfar.