I just watched all of Mitt's speech on his religion and here are my initial impressions,

* Mitt got a nice lead in from George Bush Sr., gave a generally pleasant speech, and had an enthusiastic crowd. That's a plus since it will be a heavily watched speech.

* However, the concerns that I have heard expressed about Mormonism over and over again are that it's a heretical Christian cult that has some rather strange views. Mitt didn't address those concerns at all. So, if someone had a problem with Mitt for those reasons before the speech, he probably has a problem with him after the speech as well.

* So, if Mitt didn't address the concerns people actually have about his faith, what did he do? Well, oddly enough, he sort of echoed some of the same things that Kennedy said (My church won't tell me what to do). Since that was a concern about Catholicism at the time (He might let the Pope order him around), it doesn't really seem to make sense for Mitt to discuss it.

The other thing Mitt tried to do, beyond general appeals to religious liberty, was make common cause with Christian conservatives. He said that he worshipped Jesus, just like we do, and he attempted to address a lot of the concerns that we have in general (Christianity under attack by secularism, our First Amendment rights to religious liberty being improperly taken away in the name of "separation of church and state.")

Summary: Did it help?

Well, I think he could get a bump because Mitt came across well, had a good audience, appealed to Christians, and Bush gave him a nice introduction.

On the other hand, if you were one of the people who opposed Mitt Romney because you're afraid having him as the nominee would give a boost to a heretical religion or because you think less of a guy who believes some of the weirder things that Mormons do, I'm not sure anything has changed for you since Mitt didn't address those points at all.

So, my best first guess would be that Mitt will get a temporary bump from the speech, but that it won't help him much long-term.