Apart from Bingley's feelings towards Jane, I once went through the Netherfield chapters to figure out if Elizabeth "should" have realized that Darcy was interested in her, and discovered that, on the contrary, *Bingley* was the only one who was consistently nice to her during this time.

[Elizabeth] was received, however, very politely by [the Bingley sisters]; and in their brother's manners there was something better than politeness; there was good-humour and kindness. (ch.7)

[Bingley], indeed, was the only one of the party whom [Elizabeth] could regard with any complacency. His anxiety for Jane was evident, and his attentions to herself most pleasing, and they prevented her feeling herself so much an intruder as she believed she was considered by the others. She had very little notice from any but him. (ch.8)

Even making allowances for the fact that it's never a mistake to gain the good opinion of the favourite sister of the one you are interested in ;-), IMO Bingley is being nice and friendly just because that's the kind of person he is.

Line, President and Founder of the Charles Bingley Appreciation Society :-)