I think, with equal temperament now the standard, the keys no longer really have unique feelings associated with them in any scientific sense -- other than the range of the instruments being used producibg different timbres. But people still tend to assign the keys general moods based on (or simply inspired by?) the days before equal temperament, when there were very real differences between the keys.
In Ye Olden Days, there would be quite a bit of difference in the ratio of the sound waves in, say, a major third in one key versus a major third in another key. One might be much closer to the perfect fourth interval, while another might be closer to the minor third interval. Thus, playing a piece in one key versus the other had a big difference on the mood of the result. I'm given to understand that some keys were cacophonous and pretty much unusable. When the equal temperament system came along, these subtle differences in pitch were 'flattened out' in favor of a standardized system.
On a more personal level, as a guy with a guitar who can just move a capo up the guitar neck and sing a song in whatever key I choose, I can tell you that I never choose a key for a song based on the native 'mood' of that key. It's always about finding the right key for each song for the range of my voice, and making sure that meshes well with the pitch of the guitar.