I downloaded the Desktop Pro trial with the 'Heather' voice. I told the sales rep that I'd heard good things about the product. She told me to write back after I'd tested it.
I like the voice--it's breathy, sort of Kathleen Turnerish. I, too, tried to find a 3rd-party distributor for the voice (there are none in the US). However, most of the companies I contacted didn't sell the full SAPI version of Heather; the voice worked ONLY with the utility that the company sold. No good for a Hal user.
So I went back to Infovox/Acapela. I asked the sales rep if she'd sell me a license. She said she would--for 249USD! That's a ridiculous price. The AT&T voices, which are just as good, are only 25/35USD. I pointed this out, politely, to the sales rep and asked why the product was so expensive. That was 2 weeks ago. I haven't heard back from her.
In my view, the best female voice around is AT&T's Lauren (not Crystal, the voice that intially comes with the speech engine). You can get it from TextAloud if you buy their TTS reader. TextAloud provides prompt service and good support.[/font=Verdana]