So, it is "saved from". Salvation in Islam is all about avoiding something.
Also two things are required according to this hadith:
1) testify that none has the right to be worshipped but Allah.
2) testify that Muhammad (pbuh) is his Apostle.
Not to be picky, but #1 doesn't actually say to worship Allah. Instead it says to testify that none has the right to be worshipped except Allah. There is a story that it is reported Jesus told about two sons who were asked by their father to work in the family vineyard. The first son said, "YES", but didn't actually go and work. The second said, "NO", but do go and work. Then Jesus asked which of these two sons did the will of his father. And the crowd said the second. Jesus then encouraged them to do more than just talk about God, but to actually practice the righteousness that God seeks. Surely, a Muslim most do more than just testify about Allah's right to be worshipped, he/she should also actually be worshipped? Maybe that is implied in the Hadith, but I don't see it articulated. Why is it not?
Second question arising from the Hadith, with two parts itself. Why is testifying about Muhammad's role put on par with testifying about Allah?
a) If I read correctly, this would mean that those who followed Islam before the coming of Muhammad and who both testified that none other than Allah were worthy of worship and worshipped only Allah would also have to testify with regard to Muhammad, but how could they?
b) Even if those before Muhammad were someone grandfathered in, I still don't see why one must acknowledge Muhammad personally? I can imagine one who stumbles upon the Qu'ran. Reads the Surah with regard to Allah, and makes such a testimony. But his life is cut short and he never gets around to learning about Muhammad. He just accepts what he has read as true and lives by it, but doesn't make any testimony about Muhammad. Muhammad doesn't keep one from Hell, only Allah does. Why is it necessary to make this testimony about Muhammad?