Google Now on JB is awesome. Can't see anything better than it right now.
Ahh ok cool.This is for people without jb.
I've used Dragon Mobile Assistant (called simply, "Dragon") for a while now and I really like it. It was developed by Nuance, who, incidentally, helped to develop Siri. It's in beta (will probably always be that way), a second version was recently released and it works better than the reviews are saying.
I installed it, but saw it after a Swype update. It is OK, but I have a few bones to pick with it. If it looks up an internet site for you, it won't give you the option to share the page via anything. It uses the browser to play YouTube. It's not as convenient as voice search when it comes to just entering text. With voice you can hold the mic and it opens the voice search or just tap it to type. I haven't looked at the app association list to see if search is one that you can change.??? And I don't know if it's a settings thing or an app thing, but Dragon will not make calls. It's OK for some stuff, but for the things I do a lot I still kind of prefer voice search. Although I have to admit it is much better, more betterer, than Iris. That was a joke the last time I gave it a chance. I tried it a long time ago when I first heard about it, then tried it again a little while ago thinking that it had some time to be improved and updated, but no luck. For me anyway.