Darn it - I should've read all my emails before replying to 

Muke Tever wrote:
> Classical Latin had, almost certainly:
>   /a/
>   /a:/
>   /e/  [E]
>   /e:/ [e:]
>   /i/  [I]
>   /i:/ [i:]
>   /o/  [O]
>   /o:/ [o:]
>   /u/  [U]
>   /u:/ [u:]
>   (and borrowed /y/, /y:/)

You do well to add "almost"   ;)

Without time travel we'll never be entirely certain, but the 
above clearly reflected the spoken language at some period. 
How great the qualitative differences were in the earliest 
period and in the standard literary language we'll probably 
never know.

> There was a difference in quality, but the difference wasn't phonemic, 
> any more than aspiration is phonemic in English; presumably an [E:] 
> would have been heard as [e:]

  ...or, may be as [E]  ;)

>  In fact, they certainly heard Greek eta 
> that way, though I don't know if the [E:] value of Greek eta lasted into 
> the period of classical Latin.

No, it didn't. Greek eta had already begun its journey 
towards the Byzantine & modern [i]. When they Romans 
encountered it, it had already been raised to [e:].

> Now, according to Allen's _Vox Latina_, there _was_ a distinction 
> between two types of long E in ante-classical Latin--and some vulgar 
> Latin of the classical period, which classical writers labelled as 
> "rustic"--but one of them (which had previously been written as |ei|) 
> had merged with /i:/ in Classical Latin.

Umm - I should like to see the evidence that Allen gives. 
It's true that pre-classical |ei| is just plain |i| in the 
Classical language, e.g. deico --> dico /di:ko:/ "I say". 
But I was under the impression that |ei| actually meant [ej] 
  in the pre-classical language, where in medial syllables 
earlier -ai, -ei, -oi all became -ei.

Nid rhy hen neb i ddysgu.
There's none too old to learn.