As I tried to think of things to write about Tyler, I could think of few positives about the man, at least in the view of history.
It's hard to say what public opinion would have said about him at the time. Maybe he would have been thought of by his southern colleagues as a true defender of the Republic and enemy of the 'Tyranny' of the national bank and northern meddling in southern affairs.
Now, however, the consensus view of history is that his great legacy was the following:
1) He seized power after Harrison died and maintained the presidency. (until this point, most thought that the vice president would simply serve as acting presidency until another election was arranged) He was referred to as 'His Accidency' to his death.
2) He tried to be a national cheer leader for the institution of slavery going as far as hiring foreign secret agents to promote it in London and Paris newspapers. He supported and signed the joint resolution on the acquisition of Texas to expand the slave holding republic in the South.
3) He agreed to run on the Whig ticket while refusing to adhere to almost any of the party's beliefs (internal improvements, protection of manufacturing interests etc) It was well known at the time he was nominated that he was really a Southern Democrat, but it was thought that putting him on Harrison's ticket as VP wouldn't hurt anything since even in the event of Harrison's death, he wouldn't really become president (SEE NUMBER 1)
4) When he made the decision to stay in Office, he was abandoned by both major political parties, the Whigs because he was a Democrat and the Democrats because he ran as a Whig. Except for Daniel Webster, his entire cabinet resigned.
5) He ultimately betrayed his own country, defecting to the Confederacy during the Civil War (he died soon after)
When Tyler died, the United States didn't even officially mourn his passing. I can't say I do now either.