I can confirm that Siriport works on my iPad2 although there are caveats.
First, you're installing an application and "certificate" written from an untrusted Russian source.
Second, getting authenticated can take days (honestly) due to the load on their servers.
Lastly, it's rather limited as the only way to invoke "Siri" is with a long press of the iPad's home button. There's no microphone key on the iPad's keyboard to use for dictation and some applications simply don't work properly. When Siri "finds" location based questions, you're unable to select from the screen. (i.e. "Show me the closest Pizza places" Siri will respond with, "I've found thirteen pizza restaurants, 11 are fairly close to you:" It will display the names and distances, but you don't have the ability to select one from the screen as I can with my 4S)
It does work without the proxy hassles as long as you're aware of the limitations and risks.
Probably best to wait, but I like to push things just a bit. YMMV.
