I think it's imperative that all the info available in the hand histories is included in the XML.
If that's the case I don't think there is many compelling reasons for bloating the files with the original HH.
<ul type="square"> [*]I'm not sure how including the original HH would help with compatibility breaking updates....if the parses don't manage to extract the data, in what way would it help an application that should use the data if the HH is included?
I guess the developer of the app could try to be quicker to write a functioning parser than the developer that writes the parser, but that kind of defeats the purpose of having an XML standard in the first place.
[*]If all the data originally available in the HH is there it would be easier to re-parse the XML
[*]If you want to store a hand that currently no parser supports, why not store it it's original format?
No application that expects PokerHandXML as input will be able to do anything with the data anyway, just as it will not be readable by an application expecting the raw HH.
[*]To compare output of converters or to check their accuracy just try them out with the history files.
[*]Parsing the XML into a regular HH format is not difficult if people would find a need for that.[/list]
As for the version information I think it's a good idea to include a DOCTYPE linking to a schema when one is finalized.