Others may have other reasons but this is why I don't like bit streaming:
- if you use HDMI for audio you can pass uncompressed multi-channel PCM audio to your receiver. Unlike with old s/pdif you do not need to bitstream to send full quality multi-channel audio.
- blu-ray formats used are almost always lossless. It makes no difference if they are decoded by your receiver or your PC. The result is exactly the same for True-HD provided you use red October and is for DTS-HD too if you have the Arcsoft DTS-HD decoder.
- PC graphics cards almost always have somewhat inaccurate clocks, which normally will lead to dropped repeated frames every few minutes, seen as judder. If you use red October HQ with non-bitstream audio then MC can subtly adjust video and audio timing (videoclock) to keep playback perfectly smooth for hours/days. It cannot do this with bitstreamed audio.
The big caveat, IMO, is you need that Arcsoft DTS-HD decoder. I would not want to lose high-def DTS audio. DTS is by far the most common audio format on blu-ray.