My kids were having fun with it just the other day. They wanted to make the computer say, 'Aaaaaaaaaaaaaaaaaaaa', like it was falling off a cliff, but the Mac does weird things trying to say it. (Try it directly in Safari
just right click on the word, and select 'Speech > Start Speaking'). This however works a treat: 'A a a a a a a a a a a a a a a a a a a a a a a!' Well almost!
When I was a teenager I wrote a BASIC program (well, actually cobbled one together based on someone else's program) which was a crude attempt at AI on the Commodore 64, and I even paired it up with a speech synthesiser (I think it was called 'SAM') so when the computer responded it would actually speak. It was pretty cool back in the day! This was a few years before the Mac learnt to speak anyway.
Now that I'm too old and serious for such silliness I still use the Mac's text-to-speech sometimes when I'm paying online bills and want to check that I've entered a reference number correctly. I find it easier to have the number read out while I check it against the bill.
Regarding the quality of voices, Alex was quite an improvement over the other ones, most of which have been around forever. When Alex came out, I confess to sending Apple a request for more voices of this quality
but you know, with the option for a French or Russian female voice. No harm in asking right? 🙂