I just got my first MP3-CD capable player for Christmas, and the joy of that was indeed muted by the fact that so many of my audiobooks are NOT MP3.
For books without sound effects, I always use Speex. For books with sound effects, I'd stopped using MP3 a few months ago and started using Ogg.
The only books I have in MP3 are ones that came to me already encoded as such, like those I download from AudioBooksForFree.com (Their Sherlock Holmes series is absolutely outstanding, by the way).
To my knowledge, there is NO hardware player support for Speex at all---it's too new to expect hardware support now---and I think the only reason we can even HOPE for it in the future is that Speex is one of the codecs under the Ogg umbrella.
Speaking of Speex hardware support I'm a little concerned that Speex hasn't got a 44,100Hz or maybe 48000Hz mode. Obviously 8, 16, and 32 are great modes for VoIP and similar functions, but I would have thought that for CD archiving a 44,100Hz mode would have provided for easier hardware implementation. Although I'm not technical so I could be completely wrong.
I too am hoping for a 44Khz mode, and there's no reason not to have it, since for the most part, it already exists.
The Ultra-wideband encoding will work on audio sampled at 44Khz, and the sound quality is fine, by my ears.
The real issue is simply that Speex isn't OPTIMIZED for sampling rates other than 8, 16, and 32Khz, so the effectiveness of the compression is hit or miss with other rates.
With 32KHz my Speex files almost always turn out to be significantly smaller than their MP3 counterparts. With 44Khz, the resulting file sizes vary so widely that I never know whether they're acceptable until I've encoded them. Some files have turned out significantly larger than their MP3 and Ogg counterparts.
There's a big set of lectures on CD that I'll be ripping and encoding this week, and I'll just resample the WAV files down to 32Khz for encoding.
48Khz support seems to be overkill, since that's DVD-quality sound. It may be that Jean-Marc considers even 44Hhz to be overkill for a speech codec though.