knee-jerk thoughts would be that the near-field response would not be ideal. They may be tipped up in the high frequencies a bit as they were probably designed to have appropriate high frequencies when the listener is seated 6-10+ feet away. Since high frequencies are more easily absorbed by common room furnishings than mids and bass, the manufacturer commonly raises the output of the high frequencies to compensate for this. Thus, if you are seated very close to the speakers, the room's furnishings hadn't absorbed as much highs by the time the sound hits you.
But, nothing beats trying it for yourself if you already own the speakers. Since the tweeters are horns, you would have to toe the speakers in quite a bit towards your ears to get a proper response (generally the frequency response drops off quickly outside of the angle of the horn's opening). However, you can play with the toe-in to adjust to your liking.