One additional comment around MSXML3 and MSXML6, actually.

The JScript issue you described (which is interesting, I'd like to see a 
repro of that) notwithstanding, MSXML3 is the *only* version of MSXML 
guaranteed to be on a Windows machine. As of the updates MS06-061 and 
MS06-071 in late 2006, as I said, all Windows machines have the latest 
non-Vista publically available versoin of MSXML3 now on-box. If your users 
are not using Windows update, then they have MSXML3sp5 (XPSP2) or MSXML3sp7 
(W2k3sp1).

MSXML6 is shipping on Windows Vista, and we are actively pursuing all 
available channels to push it downlevel too; but with all OS releases that 
process takes time. As part of the Xml Core team's MSXML4 EOL messaging, we 
are pushing downloading the MSXML6 redist and developing against MSXML6 for 
new software. As developers you can definitely look forward to MSXML6 
becoming more available as the year progresses.

>> As we do agree that MSXML6 is up-to-date the best choice, we'll try
>> first this library. If no luck then we will try consecutively all other
>> libraries from top to bottom. Jumping from MSXML6 right onto MSXML3 is
>> not an option: as it was explained earlier it can be Windows 98
>> SE/Windows 2000 platform with MSXML4 update so MSXML3 unavailable. Thus
>> by going from 6 right to 3 you are cutting off without any reason some
>> part of potential users.
>
> You have to realize that while your current line of argument may be true, 
> it is not relevant. The OS and security and Web landscape has moved along 
> quite a  bit since the bad old days of Windows 9x, and anyone runing these 
> OSs on the Internet has much much larger problems than their version of 
> MSXML. But, just briefly, lets address your points: Win95 and Win98 are 
> long out of support now. Windows NT 4 is as well, except for large shop 
> CSAs that get special support from my group and others. Talking about 
> these platfoms in the context of security and development is like talking 
> about ...we'll VAX or Lisa, or something inane. The first relevant 
> platform we could legitimately address in the MSXML context is Windows 
> 2000 sp4, which is the only version of Windows 2000 still in support. If 
> you are REALLY doing web development for Win9x, then I suggest you update 
> your scripts and if you are getting hit by an OS verson thats older than 
> NT5, do your client and yourself a favor and serve them some static 
> content.