I can't imagine that it would affect sound quality. I have my soffits angled at 45 degrees which I had a lot of trouble finding like examples. I've been extremely happy with them as they are less intrusive of the space and let me angle my rear and surround channles towards the listening area.
Budget Home Theater:
Denon AVR-1911 Receiver, Bic V-1220 Subwoofer, Micca MB42/C Speakers, Epson 8350 Projector, Home-made ~90" 16:9 Screen, Berkline 13175