I wrote an answer to a slightly different topic that largely covers this here.

To summarize, no but they are better than nothing.

Most of the hadith we have were written down in the Abbasid period, about 200 years after the Prophet was alive. A lot had obviously changed in that time, and since the Prophet, most of his companions, and the vast majority of contemporary Meccan/Hijazi/Arabian society were illiterate at that time, they had no direct source material to work from.

They were working off oral traditions, many of which were surely correct (Arabian society, like many illiterate societies had a more standardized/reliable form of recording oral histories then we are used to), but many of which had been fabricated (either intentionally or unintentionally) over the past centuries.

The Hadith writers also would be under lots of pressure to A) not make the Prophet look sinful or hypocritical, B) not make common practices of the Abbasid elite look counter to Mohamad's teachings and C) to give the impression that they had exhaustive knowledge about the Prophet's life, even when they did not.

All of this makes for bad history.

The Hadith (like the narrative parts of the old and new testament) aren't completely worthless for historians, but aren't the best sources either.