-Hector Berlioz from his Treatise on Orchestration
Berlioz also says this about the oboe.:
The sounds of the oboe are suitable for expressing simplicity, artless grace, gentle happiness, or the grief of a weak soul. It renders these admirably in cantabile passages.
It can also convey a degree of agitation, but one must be careful not to intensify this to cries of passion, to vehement outbursts of anger, threats or heroism: its thin, bitter-sweet tones then become feeble and altogether grotesque.
I think that Berlioz is on the right track with this. The oboe does sound best when used in the kinds of passages he describes. Here are some examples of this.