When you say its own error pages, do you mean pages presented for HTML status codes, such as 404 and 501 etc? If so, then I guess that could be the case, but I can't believe that those pages would be so advanced that they don't work in browsers earlier than IE8.
We currently use IE6 in our enterprise environment (soon to be moving to IE8) so I was really hoping to find out if I could get by with IE6 for the short period before we change over.
Is anyone out there using the 2.0 listener with browsers older then IE8, are you experiencing any issues?
I didn't test AL 2.0 with IE 6, but I don't see a reason why this shouldn't work. I think this requirement has been forwarded from APEX Listener 1 (and 1.1, respectively), which has a web based admin GUI that used CSS features IE 6 didn't implement. Possibly the current error pages may not appear well formatted if you view them in IE 6, but I don't think this would be a no-go for production.
You shoul keep in mind, that current APEX releases require at least IE 7 to work properly, at least with themes provided by these releases. But if you don't experience any issues with your APEX release, using APEX Listener 2 instead of your current web server for APEX won't make any difference.