How does the audience react to Shakespeare's portrayal of Caliban in The Tempest?
The first element of the audience reaction is to his physical presence. He is usually portrayed as awkward, uncouth, and savage. Thus he is not a sympathetic character. His admission that he tried to rape Miranda and his getting drunk are also less than admirable.
On the other hand, one can also see him as innocent and victimized, too readily trusting of outsiders to the island. There is also the issue that he is the rightful ruler of the island whose place has been usurped by Prospero, a point he makes in the lines:
This island's mine, by Sycorax my mother,
Which thou tak'st from me....
...I am all the subjects that you have,
Which first was mine own king...
In many ways we can sympathize with him as we do with other indigenous peoples displaced and oppressed by colonial powers.