Voice commands and voice talk are great, I use commands quite a lot.
It's based on Vlingo of course, and is much better than just using Google's own voice actions.
But Siri will greatly benefit from being 'hardwired' into all the Apple apps on the 4S.
I don't think we will see that kind of integration on the Galaxy 2S as Vlingo or any other developer cannot program a new voice assistant app that will be able to call upon and interact with every 3rd party email client or camera app etc etc., or anything that isn't vanilla android without spending a lot of time and development with the creators of those apps, and even then, what may work on the SG2 may not on another android phone, and that may put off devs from trying.
I think Siri will be awesome if Apple can get it working as well in day to day situations as it does in the demo videos.
I hope we do get an android equivalent, don't get me wrong, but I think its unlikely.